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.

pkg/wire/build.go

@@ -42,6 +42,8 @@ type GameView struct {
 	EndReason            string
 	Seats                []SeatView
 	LastActivityUnix     int64
+	// VsAI marks an honest-AI game (the opponent is shown as 🤖, chat/nudge/add-friend off).
+	VsAI bool
 }
 
 // TileRecord is one tile in a decoded MoveRecord (the concrete letter, "?" for a blank
@@ -158,6 +160,7 @@ func BuildGameView(b *flatbuffers.Builder, g GameView) flatbuffers.UOffsetT {
 	fb.GameViewAddEndReason(b, endReason)
 	fb.GameViewAddSeats(b, seats)
 	fb.GameViewAddLastActivityUnix(b, g.LastActivityUnix)
+	fb.GameViewAddVsAi(b, g.VsAI)
 	return fb.GameViewEnd(b)
 }