feat: honest AI opponent in quick game

New Game's quick game gains an explicit opponent selector — 🤖 AI (default)
or 👤 Random player. AI starts a game seated with a pooled robot that joins
and moves at once: no per-move timeout (a 7-day inactivity loss reusing the
turn-timeout sweeper), chat/nudge disabled, no statistics, the opponent shown
as 🤖 everywhere. The random path (disguised robot) is unchanged.

Driven by one game flag (games.vs_ai), set only on AI-started games so the
disguised path is never revealed; Matchmaker.StartVsAI seats the robot
directly (no open pool); the robot replies event-driven via the game service's
after-commit/after-create hook. Wire: vs_ai on EnqueueRequest + GameView.

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

@@ -32,8 +32,13 @@ multipleWordsPerTurn():boolean {
   return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
 }
 
+vsAi():boolean {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
+}
+
 static startEnqueueRequest(builder:flatbuffers.Builder) {
-  builder.startObject(2);
+  builder.startObject(3);
 }
 
 static addVariant(builder:flatbuffers.Builder, variantOffset:flatbuffers.Offset) {
@@ -44,15 +49,20 @@ static addMultipleWordsPerTurn(builder:flatbuffers.Builder, multipleWordsPerTurn
   builder.addFieldInt8(1, +multipleWordsPerTurn, +false);
 }
 
+static addVsAi(builder:flatbuffers.Builder, vsAi:boolean) {
+  builder.addFieldInt8(2, +vsAi, +false);
+}
+
 static endEnqueueRequest(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createEnqueueRequest(builder:flatbuffers.Builder, variantOffset:flatbuffers.Offset, multipleWordsPerTurn:boolean):flatbuffers.Offset {
+static createEnqueueRequest(builder:flatbuffers.Builder, variantOffset:flatbuffers.Offset, multipleWordsPerTurn:boolean, vsAi:boolean):flatbuffers.Offset {
   EnqueueRequest.startEnqueueRequest(builder);
   EnqueueRequest.addVariant(builder, variantOffset);
   EnqueueRequest.addMultipleWordsPerTurn(builder, multipleWordsPerTurn);
+  EnqueueRequest.addVsAi(builder, vsAi);
   return EnqueueRequest.endEnqueueRequest(builder);
 }
 }

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

@@ -98,8 +98,13 @@ lastActivityUnix():bigint {
   return offset ? this.bb!.readInt64(this.bb_pos + offset) : BigInt('0');
 }
 
+vsAi():boolean {
+  const offset = this.bb!.__offset(this.bb_pos, 28);
+  return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
+}
+
 static startGameView(builder:flatbuffers.Builder) {
-  builder.startObject(12);
+  builder.startObject(13);
 }
 
 static addId(builder:flatbuffers.Builder, idOffset:flatbuffers.Offset) {
@@ -162,12 +167,16 @@ static addLastActivityUnix(builder:flatbuffers.Builder, lastActivityUnix:bigint)
   builder.addFieldInt64(11, lastActivityUnix, BigInt('0'));
 }
 
+static addVsAi(builder:flatbuffers.Builder, vsAi:boolean) {
+  builder.addFieldInt8(12, +vsAi, +false);
+}
+
 static endGameView(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createGameView(builder:flatbuffers.Builder, idOffset:flatbuffers.Offset, variantOffset:flatbuffers.Offset, dictVersionOffset:flatbuffers.Offset, statusOffset:flatbuffers.Offset, players:number, toMove:number, turnTimeoutSecs:number, multipleWordsPerTurn:boolean, moveCount:number, endReasonOffset:flatbuffers.Offset, seatsOffset:flatbuffers.Offset, lastActivityUnix:bigint):flatbuffers.Offset {
+static createGameView(builder:flatbuffers.Builder, idOffset:flatbuffers.Offset, variantOffset:flatbuffers.Offset, dictVersionOffset:flatbuffers.Offset, statusOffset:flatbuffers.Offset, players:number, toMove:number, turnTimeoutSecs:number, multipleWordsPerTurn:boolean, moveCount:number, endReasonOffset:flatbuffers.Offset, seatsOffset:flatbuffers.Offset, lastActivityUnix:bigint, vsAi:boolean):flatbuffers.Offset {
   GameView.startGameView(builder);
   GameView.addId(builder, idOffset);
   GameView.addVariant(builder, variantOffset);
@@ -181,6 +190,7 @@ static createGameView(builder:flatbuffers.Builder, idOffset:flatbuffers.Offset,
   GameView.addEndReason(builder, endReasonOffset);
   GameView.addSeats(builder, seatsOffset);
   GameView.addLastActivityUnix(builder, lastActivityUnix);
+  GameView.addVsAi(builder, vsAi);
   return GameView.endGameView(builder);
 }
 }