Stage 13: alphabet on the wire (UI alphabet-agnostic, TODO-4)

Live play now exchanges per-variant alphabet indices instead of concrete
letters (rack out; submit-play, evaluate, exchange, word-check in). The client
caches each variant's (index, letter, value) table behind
StateRequest.include_alphabet and renders the rack and blank chooser from it,
dropping the hardcoded value/alphabet tables. History, the durable journal and
GCG stay decoded concrete characters (ARCHITECTURE §9.1, unchanged).

- pkg/fbs: new AlphabetEntry + PlayTile; StateView.rack -> [ubyte] + alphabet;
  StateRequest.include_alphabet; SubmitPlay/Eval tiles -> [PlayTile];
  Exchange tiles + CheckWord word -> [ubyte] (committed Go + TS regenerated).
- engine: AlphabetTable + a cached per-variant codec (LetterForIndex/EncodeRack/
  DecodeTiles/DecodeWord) + BlankIndex sentinel; Go parity test.
- backend server edge maps index<->letter (new thin game.Service.GameVariant);
  game.Service domain methods, engine.Game and the robot keep one letter-based
  play path. The gateway forwards indices verbatim (no alphabet table).
- ui: lib/alphabet.ts in-memory cache; codec encodes/decodes indices; premiums.ts
  is geometry-only; the mock seeds a fixture table; the UI normalises display to
  upper case (codec + cache), leaving placement/board/checkword unchanged.

Parity moved to the Go engine.AlphabetTable test; premiums.ts loses its value
tables. Discharges TODO-4.

ui/src/gen/fbs/scrabblefb.ts

@@ -2,6 +2,7 @@
 
 export { AccountRef } from './scrabblefb/account-ref.js';
 export { Ack } from './scrabblefb/ack.js';
+export { AlphabetEntry } from './scrabblefb/alphabet-entry.js';
 export { BlockList } from './scrabblefb/block-list.js';
 export { ChatList } from './scrabblefb/chat-list.js';
 export { ChatMessage } from './scrabblefb/chat-message.js';
@@ -41,6 +42,7 @@ export { MoveResult } from './scrabblefb/move-result.js';
 export { NotificationEvent } from './scrabblefb/notification-event.js';
 export { NudgeEvent } from './scrabblefb/nudge-event.js';
 export { OpponentMovedEvent } from './scrabblefb/opponent-moved-event.js';
+export { PlayTile } from './scrabblefb/play-tile.js';
 export { Profile } from './scrabblefb/profile.js';
 export { RedeemCodeRequest } from './scrabblefb/redeem-code-request.js';
 export { RedeemResult } from './scrabblefb/redeem-result.js';

ui/src/gen/fbs/scrabblefb/alphabet-entry.ts

@@ -0,0 +1,68 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+import * as flatbuffers from 'flatbuffers';
+
+export class AlphabetEntry {
+  bb: flatbuffers.ByteBuffer|null = null;
+  bb_pos = 0;
+  __init(i:number, bb:flatbuffers.ByteBuffer):AlphabetEntry {
+  this.bb_pos = i;
+  this.bb = bb;
+  return this;
+}
+
+static getRootAsAlphabetEntry(bb:flatbuffers.ByteBuffer, obj?:AlphabetEntry):AlphabetEntry {
+  return (obj || new AlphabetEntry()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+static getSizePrefixedRootAsAlphabetEntry(bb:flatbuffers.ByteBuffer, obj?:AlphabetEntry):AlphabetEntry {
+  bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+  return (obj || new AlphabetEntry()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+index():number {
+  const offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readUint8(this.bb_pos + offset) : 0;
+}
+
+letter():string|null
+letter(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+letter(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+value():number {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
+}
+
+static startAlphabetEntry(builder:flatbuffers.Builder) {
+  builder.startObject(3);
+}
+
+static addIndex(builder:flatbuffers.Builder, index:number) {
+  builder.addFieldInt8(0, index, 0);
+}
+
+static addLetter(builder:flatbuffers.Builder, letterOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(1, letterOffset, 0);
+}
+
+static addValue(builder:flatbuffers.Builder, value:number) {
+  builder.addFieldInt32(2, value, 0);
+}
+
+static endAlphabetEntry(builder:flatbuffers.Builder):flatbuffers.Offset {
+  const offset = builder.endObject();
+  return offset;
+}
+
+static createAlphabetEntry(builder:flatbuffers.Builder, index:number, letterOffset:flatbuffers.Offset, value:number):flatbuffers.Offset {
+  AlphabetEntry.startAlphabetEntry(builder);
+  AlphabetEntry.addIndex(builder, index);
+  AlphabetEntry.addLetter(builder, letterOffset);
+  AlphabetEntry.addValue(builder, value);
+  return AlphabetEntry.endAlphabetEntry(builder);
+}
+}

ui/src/gen/fbs/scrabblefb/check-word-request.ts

@@ -27,11 +27,19 @@ gameId(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
-word():string|null
-word(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
-word(optionalEncoding?:any):string|Uint8Array|null {
+word(index: number):number|null {
   const offset = this.bb!.__offset(this.bb_pos, 6);
-  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+  return offset ? this.bb!.readUint8(this.bb!.__vector(this.bb_pos + offset) + index) : 0;
+}
+
+wordLength():number {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
+}
+
+wordArray():Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? new Uint8Array(this.bb!.bytes().buffer, this.bb!.bytes().byteOffset + this.bb!.__vector(this.bb_pos + offset), this.bb!.__vector_len(this.bb_pos + offset)) : null;
 }
 
 static startCheckWordRequest(builder:flatbuffers.Builder) {
@@ -46,6 +54,18 @@ static addWord(builder:flatbuffers.Builder, wordOffset:flatbuffers.Offset) {
   builder.addFieldOffset(1, wordOffset, 0);
 }
 
+static createWordVector(builder:flatbuffers.Builder, data:number[]|Uint8Array):flatbuffers.Offset {
+  builder.startVector(1, data.length, 1);
+  for (let i = data.length - 1; i >= 0; i--) {
+    builder.addInt8(data[i]!);
+  }
+  return builder.endVector();
+}
+
+static startWordVector(builder:flatbuffers.Builder, numElems:number) {
+  builder.startVector(1, numElems, 1);
+}
+
 static endCheckWordRequest(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;

ui/src/gen/fbs/scrabblefb/eval-request.ts

@@ -2,7 +2,7 @@
 
 import * as flatbuffers from 'flatbuffers';
 
-import { TileRecord } from '../scrabblefb/tile-record.js';
+import { PlayTile } from '../scrabblefb/play-tile.js';
 
 
 export class EvalRequest {
@@ -37,9 +37,9 @@ dir(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
-tiles(index: number, obj?:TileRecord):TileRecord|null {
+tiles(index: number, obj?:PlayTile):PlayTile|null {
   const offset = this.bb!.__offset(this.bb_pos, 8);
-  return offset ? (obj || new TileRecord()).__init(this.bb!.__indirect(this.bb!.__vector(this.bb_pos + offset) + index * 4), this.bb!) : null;
+  return offset ? (obj || new PlayTile()).__init(this.bb!.__indirect(this.bb!.__vector(this.bb_pos + offset) + index * 4), this.bb!) : null;
 }
 
 tilesLength():number {

ui/src/gen/fbs/scrabblefb/exchange-request.ts

@@ -27,11 +27,9 @@ gameId(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
-tiles(index: number):string
-tiles(index: number,optionalEncoding:flatbuffers.Encoding):string|Uint8Array
-tiles(index: number,optionalEncoding?:any):string|Uint8Array|null {
+tiles(index: number):number|null {
   const offset = this.bb!.__offset(this.bb_pos, 6);
-  return offset ? this.bb!.__string(this.bb!.__vector(this.bb_pos + offset) + index * 4, optionalEncoding) : null;
+  return offset ? this.bb!.readUint8(this.bb!.__vector(this.bb_pos + offset) + index) : 0;
 }
 
 tilesLength():number {
@@ -39,6 +37,11 @@ tilesLength():number {
   return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
 }
 
+tilesArray():Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? new Uint8Array(this.bb!.bytes().buffer, this.bb!.bytes().byteOffset + this.bb!.__vector(this.bb_pos + offset), this.bb!.__vector_len(this.bb_pos + offset)) : null;
+}
+
 static startExchangeRequest(builder:flatbuffers.Builder) {
   builder.startObject(2);
 }
@@ -51,16 +54,16 @@ static addTiles(builder:flatbuffers.Builder, tilesOffset:flatbuffers.Offset) {
   builder.addFieldOffset(1, tilesOffset, 0);
 }
 
-static createTilesVector(builder:flatbuffers.Builder, data:flatbuffers.Offset[]):flatbuffers.Offset {
-  builder.startVector(4, data.length, 4);
+static createTilesVector(builder:flatbuffers.Builder, data:number[]|Uint8Array):flatbuffers.Offset {
+  builder.startVector(1, data.length, 1);
   for (let i = data.length - 1; i >= 0; i--) {
-    builder.addOffset(data[i]!);
+    builder.addInt8(data[i]!);
   }
   return builder.endVector();
 }
 
 static startTilesVector(builder:flatbuffers.Builder, numElems:number) {
-  builder.startVector(4, numElems, 4);
+  builder.startVector(1, numElems, 1);
 }
 
 static endExchangeRequest(builder:flatbuffers.Builder):flatbuffers.Offset {

ui/src/gen/fbs/scrabblefb/play-tile.ts

@@ -0,0 +1,76 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+import * as flatbuffers from 'flatbuffers';
+
+export class PlayTile {
+  bb: flatbuffers.ByteBuffer|null = null;
+  bb_pos = 0;
+  __init(i:number, bb:flatbuffers.ByteBuffer):PlayTile {
+  this.bb_pos = i;
+  this.bb = bb;
+  return this;
+}
+
+static getRootAsPlayTile(bb:flatbuffers.ByteBuffer, obj?:PlayTile):PlayTile {
+  return (obj || new PlayTile()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+static getSizePrefixedRootAsPlayTile(bb:flatbuffers.ByteBuffer, obj?:PlayTile):PlayTile {
+  bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+  return (obj || new PlayTile()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+row():number {
+  const offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
+}
+
+col():number {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
+}
+
+letter():number {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.readUint8(this.bb_pos + offset) : 0;
+}
+
+blank():boolean {
+  const offset = this.bb!.__offset(this.bb_pos, 10);
+  return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
+}
+
+static startPlayTile(builder:flatbuffers.Builder) {
+  builder.startObject(4);
+}
+
+static addRow(builder:flatbuffers.Builder, row:number) {
+  builder.addFieldInt32(0, row, 0);
+}
+
+static addCol(builder:flatbuffers.Builder, col:number) {
+  builder.addFieldInt32(1, col, 0);
+}
+
+static addLetter(builder:flatbuffers.Builder, letter:number) {
+  builder.addFieldInt8(2, letter, 0);
+}
+
+static addBlank(builder:flatbuffers.Builder, blank:boolean) {
+  builder.addFieldInt8(3, +blank, +false);
+}
+
+static endPlayTile(builder:flatbuffers.Builder):flatbuffers.Offset {
+  const offset = builder.endObject();
+  return offset;
+}
+
+static createPlayTile(builder:flatbuffers.Builder, row:number, col:number, letter:number, blank:boolean):flatbuffers.Offset {
+  PlayTile.startPlayTile(builder);
+  PlayTile.addRow(builder, row);
+  PlayTile.addCol(builder, col);
+  PlayTile.addLetter(builder, letter);
+  PlayTile.addBlank(builder, blank);
+  return PlayTile.endPlayTile(builder);
+}
+}

ui/src/gen/fbs/scrabblefb/state-request.ts

@@ -27,22 +27,32 @@ gameId(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
+includeAlphabet():boolean {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
+}
+
 static startStateRequest(builder:flatbuffers.Builder) {
-  builder.startObject(1);
+  builder.startObject(2);
 }
 
 static addGameId(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset) {
   builder.addFieldOffset(0, gameIdOffset, 0);
 }
 
+static addIncludeAlphabet(builder:flatbuffers.Builder, includeAlphabet:boolean) {
+  builder.addFieldInt8(1, +includeAlphabet, +false);
+}
+
 static endStateRequest(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createStateRequest(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset):flatbuffers.Offset {
+static createStateRequest(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset, includeAlphabet:boolean):flatbuffers.Offset {
   StateRequest.startStateRequest(builder);
   StateRequest.addGameId(builder, gameIdOffset);
+  StateRequest.addIncludeAlphabet(builder, includeAlphabet);
   return StateRequest.endStateRequest(builder);
 }
 }

ui/src/gen/fbs/scrabblefb/state-view.ts

@@ -2,6 +2,7 @@
 
 import * as flatbuffers from 'flatbuffers';
 
+import { AlphabetEntry } from '../scrabblefb/alphabet-entry.js';
 import { GameView } from '../scrabblefb/game-view.js';
 
 
@@ -33,11 +34,9 @@ seat():number {
   return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
 }
 
-rack(index: number):string
-rack(index: number,optionalEncoding:flatbuffers.Encoding):string|Uint8Array
-rack(index: number,optionalEncoding?:any):string|Uint8Array|null {
+rack(index: number):number|null {
   const offset = this.bb!.__offset(this.bb_pos, 8);
-  return offset ? this.bb!.__string(this.bb!.__vector(this.bb_pos + offset) + index * 4, optionalEncoding) : null;
+  return offset ? this.bb!.readUint8(this.bb!.__vector(this.bb_pos + offset) + index) : 0;
 }
 
 rackLength():number {
@@ -45,6 +44,11 @@ rackLength():number {
   return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
 }
 
+rackArray():Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? new Uint8Array(this.bb!.bytes().buffer, this.bb!.bytes().byteOffset + this.bb!.__vector(this.bb_pos + offset), this.bb!.__vector_len(this.bb_pos + offset)) : null;
+}
+
 bagLen():number {
   const offset = this.bb!.__offset(this.bb_pos, 10);
   return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
@@ -55,8 +59,18 @@ hintsRemaining():number {
   return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
 }
 
+alphabet(index: number, obj?:AlphabetEntry):AlphabetEntry|null {
+  const offset = this.bb!.__offset(this.bb_pos, 14);
+  return offset ? (obj || new AlphabetEntry()).__init(this.bb!.__indirect(this.bb!.__vector(this.bb_pos + offset) + index * 4), this.bb!) : null;
+}
+
+alphabetLength():number {
+  const offset = this.bb!.__offset(this.bb_pos, 14);
+  return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
+}
+
 static startStateView(builder:flatbuffers.Builder) {
-  builder.startObject(5);
+  builder.startObject(6);
 }
 
 static addGame(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offset) {
@@ -71,16 +85,16 @@ static addRack(builder:flatbuffers.Builder, rackOffset:flatbuffers.Offset) {
   builder.addFieldOffset(2, rackOffset, 0);
 }
 
-static createRackVector(builder:flatbuffers.Builder, data:flatbuffers.Offset[]):flatbuffers.Offset {
-  builder.startVector(4, data.length, 4);
+static createRackVector(builder:flatbuffers.Builder, data:number[]|Uint8Array):flatbuffers.Offset {
+  builder.startVector(1, data.length, 1);
   for (let i = data.length - 1; i >= 0; i--) {
-    builder.addOffset(data[i]!);
+    builder.addInt8(data[i]!);
   }
   return builder.endVector();
 }
 
 static startRackVector(builder:flatbuffers.Builder, numElems:number) {
-  builder.startVector(4, numElems, 4);
+  builder.startVector(1, numElems, 1);
 }
 
 static addBagLen(builder:flatbuffers.Builder, bagLen:number) {
@@ -91,18 +105,35 @@ static addHintsRemaining(builder:flatbuffers.Builder, hintsRemaining:number) {
   builder.addFieldInt32(4, hintsRemaining, 0);
 }
 
+static addAlphabet(builder:flatbuffers.Builder, alphabetOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(5, alphabetOffset, 0);
+}
+
+static createAlphabetVector(builder:flatbuffers.Builder, data:flatbuffers.Offset[]):flatbuffers.Offset {
+  builder.startVector(4, data.length, 4);
+  for (let i = data.length - 1; i >= 0; i--) {
+    builder.addOffset(data[i]!);
+  }
+  return builder.endVector();
+}
+
+static startAlphabetVector(builder:flatbuffers.Builder, numElems:number) {
+  builder.startVector(4, numElems, 4);
+}
+
 static endStateView(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createStateView(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offset, seat:number, rackOffset:flatbuffers.Offset, bagLen:number, hintsRemaining:number):flatbuffers.Offset {
+static createStateView(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offset, seat:number, rackOffset:flatbuffers.Offset, bagLen:number, hintsRemaining:number, alphabetOffset:flatbuffers.Offset):flatbuffers.Offset {
   StateView.startStateView(builder);
   StateView.addGame(builder, gameOffset);
   StateView.addSeat(builder, seat);
   StateView.addRack(builder, rackOffset);
   StateView.addBagLen(builder, bagLen);
   StateView.addHintsRemaining(builder, hintsRemaining);
+  StateView.addAlphabet(builder, alphabetOffset);
   return StateView.endStateView(builder);
 }
 }

ui/src/gen/fbs/scrabblefb/submit-play-request.ts

@@ -2,7 +2,7 @@
 
 import * as flatbuffers from 'flatbuffers';
 
-import { TileRecord } from '../scrabblefb/tile-record.js';
+import { PlayTile } from '../scrabblefb/play-tile.js';
 
 
 export class SubmitPlayRequest {
@@ -37,9 +37,9 @@ dir(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
-tiles(index: number, obj?:TileRecord):TileRecord|null {
+tiles(index: number, obj?:PlayTile):PlayTile|null {
   const offset = this.bb!.__offset(this.bb_pos, 8);
-  return offset ? (obj || new TileRecord()).__init(this.bb!.__indirect(this.bb!.__vector(this.bb_pos + offset) + index * 4), this.bb!) : null;
+  return offset ? (obj || new PlayTile()).__init(this.bb!.__indirect(this.bb!.__vector(this.bb_pos + offset) + index * 4), this.bb!) : null;
 }
 
 tilesLength():number {