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.

backend/internal/game/service.go

@@ -39,8 +39,14 @@ type Service struct {
 	clock   func() time.Time
 	rng     func() int64
 	pub     notify.Publisher
-	metrics *gameMetrics
-	log     *zap.Logger
+	// aiTrigger, when set, is called after an honest-AI game is created or advanced and
+	// is still on a robot's potential turn, so the robot replies at once instead of
+	// waiting for the next driver scan. It is fire-and-forget (the robot package wires
+	// its asynchronous TriggerMove); nil disables the fast path (the scan still covers
+	// these games). Kept as a func so the game package never imports the robot package.
+	aiTrigger func(gameID uuid.UUID)
+	metrics   *gameMetrics
+	log       *zap.Logger
 }
 
 // NewService constructs a Service. store and accounts wrap the same pool;
@@ -75,6 +81,23 @@ func (svc *Service) SetNotifier(p notify.Publisher) {
 	}
 }
 
+// SetAITrigger installs the honest-AI fast-move hook called when a vs_ai game is
+// created or advanced and a robot may now be on the clock. It must be called during
+// startup wiring; the default (nil) leaves only the periodic driver scan. The robot
+// package wires its asynchronous TriggerMove here.
+func (svc *Service) SetAITrigger(trigger func(gameID uuid.UUID)) {
+	svc.aiTrigger = trigger
+}
+
+// triggerAI fires the honest-AI fast-move hook for an active vs_ai game (best-effort,
+// fire-and-forget). It is a no-op for non-AI games, finished games and when no hook is
+// installed, so callers can invoke it unconditionally after a create or commit.
+func (svc *Service) triggerAI(g Game) {
+	if svc.aiTrigger != nil && g.VsAI && g.Status == StatusActive {
+		svc.aiTrigger(g.ID)
+	}
+}
+
 // activeVersion returns the dictionary version new games currently pin.
 func (svc *Service) activeVersion() string {
 	svc.verMu.RLock()
@@ -143,11 +166,17 @@ func (svc *Service) Create(ctx context.Context, params CreateParams) (Game, erro
 		return Game{}, fmt.Errorf("%w: hints per player must be >= 0", ErrInvalidConfig)
 	}
 	timeout := params.TurnTimeout
-	if timeout == 0 {
-		timeout = DefaultTurnTimeout
-	}
-	if !allowedTimeout(timeout) {
-		return Game{}, fmt.Errorf("%w: turn timeout %s not allowed", ErrInvalidConfig, timeout)
+	if params.VsAI {
+		// Honest-AI games use the fixed 7-day inactivity clock, not a user-chosen value
+		// from AllowedTurnTimeouts (it is never offered in the creation UI).
+		timeout = AIInactivityTimeout
+	} else {
+		if timeout == 0 {
+			timeout = DefaultTurnTimeout
+		}
+		if !allowedTimeout(timeout) {
+			return Game{}, fmt.Errorf("%w: turn timeout %s not allowed", ErrInvalidConfig, timeout)
+		}
 	}
 	seen := make(map[uuid.UUID]bool, len(params.Seats))
 	for _, id := range params.Seats {
@@ -200,13 +229,21 @@ func (svc *Service) Create(ctx context.Context, params CreateParams) (Game, erro
 		hintsPerPlayer:       params.HintsPerPlayer,
 		dropoutTiles:         params.DropoutTiles.String(),
 		multipleWordsPerTurn: params.MultipleWordsPerTurn,
+		vsAI:                 params.VsAI,
 	}
 	if err := svc.store.CreateGame(ctx, ins, params.Seats); err != nil {
 		return Game{}, err
 	}
 	svc.cache.put(id, g, params.Variant.String())
 	svc.metrics.recordStarted(ctx, params.Variant)
-	return svc.store.GetGame(ctx, id)
+	created, err := svc.store.GetGame(ctx, id)
+	if err != nil {
+		return Game{}, err
+	}
+	// Honest-AI game seated with a robot: if the robot moves first, reply at once
+	// (the periodic driver is the fallback). No-op for every human-only game.
+	svc.triggerAI(created)
+	return created, nil
 }
 
 // OpenOrJoin enters accountID into auto-match for the variant and per-turn rule in
@@ -368,7 +405,7 @@ func (svc *Service) Resign(ctx context.Context, gameID, accountID uuid.UUID) (Mo
 	if err != nil {
 		return MoveResult{}, err
 	}
-	post, err := svc.commit(ctx, gameID, g, rec, rec.Action.String(), rackBefore, nil, pre.Seats)
+	post, err := svc.commit(ctx, gameID, g, rec, rec.Action.String(), rackBefore, nil, pre.Seats, pre.VsAI)
 	if err != nil {
 		return MoveResult{}, err
 	}
@@ -516,7 +553,7 @@ func (svc *Service) transition(ctx context.Context, gameID, accountID uuid.UUID,
 	if err != nil {
 		return MoveResult{}, err
 	}
-	post, err := svc.commit(ctx, gameID, g, rec, rec.Action.String(), rackBefore, exchanged, pre.Seats)
+	post, err := svc.commit(ctx, gameID, g, rec, rec.Action.String(), rackBefore, exchanged, pre.Seats, pre.VsAI)
 	if err != nil {
 		return MoveResult{}, err
 	}
@@ -546,7 +583,7 @@ func (svc *Service) afterCommitDrafts(ctx context.Context, gameID, accountID uui
 // cursor and scores, and on a game-ending move the finish stamp and statistics.
 // On a persistence failure it evicts the now-divergent live game so the next
 // access rebuilds from the journal.
-func (svc *Service) commit(ctx context.Context, gameID uuid.UUID, g *engine.Game, rec engine.MoveRecord, action string, rackBefore, exchanged []string, seats []Seat) (Game, error) {
+func (svc *Service) commit(ctx context.Context, gameID uuid.UUID, g *engine.Game, rec engine.MoveRecord, action string, rackBefore, exchanged []string, seats []Seat, vsAI bool) (Game, error) {
 	now := svc.clock()
 	logLen := len(g.Log())
 	scores := make([]int, g.Players())
@@ -577,12 +614,16 @@ func (svc *Service) commit(ctx context.Context, gameID uuid.UUID, g *engine.Game
 			c.endReason = "timeout"
 		}
 		c.winner = g.Result().Winner
-		statSeats, err := svc.nonGuestSeats(ctx, seats)
-		if err != nil {
-			svc.cache.remove(gameID)
-			return Game{}, err
+		// Honest-AI games are practice and never touch player statistics (like guest
+		// games); a human game records them for its non-guest seats.
+		if !vsAI {
+			statSeats, err := svc.nonGuestSeats(ctx, seats)
+			if err != nil {
+				svc.cache.remove(gameID)
+				return Game{}, err
+			}
+			c.stats = buildStats(g, statSeats)
 		}
-		c.stats = buildStats(g, statSeats)
 	}
 	if err := svc.store.CommitMove(ctx, c); err != nil {
 		svc.cache.remove(gameID)
@@ -596,6 +637,9 @@ func (svc *Service) commit(ctx context.Context, gameID uuid.UUID, g *engine.Game
 		return Game{}, err
 	}
 	svc.emitMove(ctx, post, rec, g.BagLen())
+	// Honest-AI game still going: nudge the robot to take its turn at once (the
+	// periodic driver is the fallback). No-op for human games and finished ones.
+	svc.triggerAI(post)
 	return post, nil
 }
 
@@ -630,6 +674,9 @@ func (svc *Service) emitMove(ctx context.Context, post Game, rec engine.MoveReco
 				word = rec.Words[0]
 			}
 			opponent := svc.displayName(ctx, post.Seats, rec.Player)
+			if post.VsAI {
+				opponent = aiOpponentName // the player chose an AI game; show the robot as 🤖, not its pool name
+			}
 			yourTurn := notify.YourTurn(next, post.ID, deadline, opponent, action, word, scoreLine(post, post.ToMove), post.MoveCount)
 			yourTurn.Language = lang
 			intents = append(intents, yourTurn)
@@ -759,7 +806,7 @@ func (svc *Service) timeoutGame(ctx context.Context, gameID uuid.UUID, now time.
 	if err != nil {
 		return false, err
 	}
-	if _, err := svc.commit(ctx, gameID, g, rec, "timeout", rackBefore, nil, cur.Seats); err != nil {
+	if _, err := svc.commit(ctx, gameID, g, rec, "timeout", rackBefore, nil, cur.Seats, cur.VsAI); err != nil {
 		return false, err
 	}
 	svc.metrics.recordAbandoned(ctx, cur.Variant)
@@ -996,6 +1043,20 @@ func (svc *Service) RobotTurns(ctx context.Context, robotIDs []uuid.UUID) ([]Rob
 	return svc.store.RobotTurns(ctx, robotIDs)
 }
 
+// RobotTurn returns the robot driver's view of a single active game seating one of
+// robotIDs, and true, or false when the game holds no pooled robot or is no longer
+// active. It backs the honest-AI fast-move trigger, which drives just the one game.
+func (svc *Service) RobotTurn(ctx context.Context, gameID uuid.UUID, robotIDs []uuid.UUID) (RobotTurn, bool, error) {
+	return svc.store.RobotTurnByGame(ctx, gameID, robotIDs)
+}
+
+// VsAI reports whether a game is an honest-AI game (games.vs_ai). The social
+// service uses it to reject chat and nudge in AI games (which otherwise report
+// status 'active').
+func (svc *Service) VsAI(ctx context.Context, gameID uuid.UUID) (bool, error) {
+	return svc.store.GameVsAI(ctx, gameID)
+}
+
 // GameState returns a seated player's view of the game: the shared summary plus
 // their private rack, the bag size and their remaining hint budget.
 func (svc *Service) GameState(ctx context.Context, gameID, accountID uuid.UUID) (StateView, error) {