R4: push enrichment — events carry a state delta, kill the last poll

Enrich the in-app live stream into a delta channel so the UI renders a move from the event without a follow-up game.state, and make the matchmaking poll a stream-down fallback.

- pkg/fbs: trailing fields on opponent_moved (move+game+bag_len), your_turn (move_count), match_found (state), game_over (game), notify (account/invitation/state), MoveResult (rack+bag_len); regenerate Go + TS.
- backend: notify owns the FB encoding (encode.go + payload.go input structs); game/lobby/social map their domain types in. emitMove builds the move delta; game.Service.InitialState feeds match_found/game_started the recipient's initial StateView; friends/invitations notify carry their account/invitation. The move-commit response (submit_play/pass/exchange/resign) returns the actor's refilled rack + bag size.
- gateway: MoveResult transcode carries rack+bag_len.
- ui: pure lib/gamedelta.ts reducer advances the per-game cache keyed on move_count (idempotent + gap-safe); app.svelte seeds the cache on match_found/game_started; Game.svelte applies the delta (commit/pass/exchange/resign drop their load()); NewGame polls only while app.streamAlive is false.
- docs: ARCHITECTURE §10, FUNCTIONAL(+ru), backend/gateway/ui READMEs; PRERELEASE R4 marked done + Refinements.

ui/src/gen/fbs/scrabblefb/opponent-moved-event.ts

@@ -2,6 +2,10 @@
 
 import * as flatbuffers from 'flatbuffers';
 
+import { GameView } from '../scrabblefb/game-view.js';
+import { MoveRecord } from '../scrabblefb/move-record.js';
+
+
 export class OpponentMovedEvent {
   bb: flatbuffers.ByteBuffer|null = null;
   bb_pos = 0;
@@ -49,8 +53,23 @@ total():number {
   return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
 }
 
+move(obj?:MoveRecord):MoveRecord|null {
+  const offset = this.bb!.__offset(this.bb_pos, 14);
+  return offset ? (obj || new MoveRecord()).__init(this.bb!.__indirect(this.bb_pos + offset), this.bb!) : null;
+}
+
+game(obj?:GameView):GameView|null {
+  const offset = this.bb!.__offset(this.bb_pos, 16);
+  return offset ? (obj || new GameView()).__init(this.bb!.__indirect(this.bb_pos + offset), this.bb!) : null;
+}
+
+bagLen():number {
+  const offset = this.bb!.__offset(this.bb_pos, 18);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
+}
+
 static startOpponentMovedEvent(builder:flatbuffers.Builder) {
-  builder.startObject(5);
+  builder.startObject(8);
 }
 
 static addGameId(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset) {
@@ -73,18 +92,21 @@ static addTotal(builder:flatbuffers.Builder, total:number) {
   builder.addFieldInt32(4, total, 0);
 }
 
+static addMove(builder:flatbuffers.Builder, moveOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(5, moveOffset, 0);
+}
+
+static addGame(builder:flatbuffers.Builder, gameOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(6, gameOffset, 0);
+}
+
+static addBagLen(builder:flatbuffers.Builder, bagLen:number) {
+  builder.addFieldInt32(7, bagLen, 0);
+}
+
 static endOpponentMovedEvent(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createOpponentMovedEvent(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset, seat:number, actionOffset:flatbuffers.Offset, score:number, total:number):flatbuffers.Offset {
-  OpponentMovedEvent.startOpponentMovedEvent(builder);
-  OpponentMovedEvent.addGameId(builder, gameIdOffset);
-  OpponentMovedEvent.addSeat(builder, seat);
-  OpponentMovedEvent.addAction(builder, actionOffset);
-  OpponentMovedEvent.addScore(builder, score);
-  OpponentMovedEvent.addTotal(builder, total);
-  return OpponentMovedEvent.endOpponentMovedEvent(builder);
-}
 }