ui/phase-25: backend turn-cutoff guard + auto-pause + UI sync protocol

Backend now owns the turn-cutoff and pause guards the order tab
relies on: the scheduler flips runtime_status between
generation_in_progress and running around every engine tick, a
failed tick auto-pauses the game through OnRuntimeSnapshot, and a
new game.paused notification kind fans out alongside
game.turn.ready. The user-games handlers reject submits with
HTTP 409 turn_already_closed or game_paused depending on the
runtime state.

UI delegates auto-sync to a new OrderQueue: offline detection,
single retry on reconnect, conflict / paused classification.
OrderDraftStore surfaces conflictBanner / pausedBanner runes,
clears them on local mutation or on a game.turn.ready push via
resetForNewTurn. The order tab renders the matching banners and
the new conflict per-row badge; i18n bundles cover en + ru.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/internal/lobby/runtime_hooks.go

@@ -37,6 +37,7 @@ func (s *Service) OnRuntimeSnapshot(ctx context.Context, gameID uuid.UUID, snaps
 	if err != nil {
 		return err
 	}
+	transitionedToPaused := false
 	if next, transition := nextStatusFromSnapshot(updated.Status, snapshot); transition {
 		switch next {
 		case GameStatusFinished:
@@ -53,12 +54,18 @@ func (s *Service) OnRuntimeSnapshot(ctx context.Context, gameID uuid.UUID, snaps
 				return err
 			}
 			updated = rec
+			if next == GameStatusPaused {
+				transitionedToPaused = true
+			}
 		}
 	}
 	s.deps.Cache.PutGame(updated)
 	if merged.CurrentTurn > prevTurn {
 		s.publishTurnReady(ctx, gameID, merged.CurrentTurn)
 	}
+	if transitionedToPaused {
+		s.publishGamePaused(ctx, gameID, merged.CurrentTurn, snapshot.RuntimeStatus)
+	}
 	return nil
 }
 
@@ -106,6 +113,56 @@ func (s *Service) publishTurnReady(ctx context.Context, gameID uuid.UUID, turn i
 	}
 }
 
+// publishGamePaused fans out a `game.paused` notification to every
+// active member of the game when the lobby flips the game to
+// `paused` in reaction to a runtime snapshot (typically a failed
+// turn generation). The intent is best-effort: a publisher failure
+// is logged at warn level and does not abort the snapshot
+// bookkeeping. Idempotency is anchored on (game_id, turn) so a
+// repeated `generation_failed` snapshot for the same turn collapses
+// into a single notification at the notification.Submit boundary.
+//
+// reason carries the raw runtime status that triggered the pause
+// (`engine_unreachable` / `generation_failed`); the UI displays a
+// status-agnostic banner today but the payload is preserved so a
+// future revision of the order tab can differentiate.
+func (s *Service) publishGamePaused(ctx context.Context, gameID uuid.UUID, turn int32, reason string) {
+	memberships, err := s.deps.Store.ListMembershipsForGame(ctx, gameID)
+	if err != nil {
+		s.deps.Logger.Warn("game-paused notification: list memberships failed",
+			zap.String("game_id", gameID.String()),
+			zap.Int32("turn", turn),
+			zap.Error(err))
+		return
+	}
+	recipients := make([]uuid.UUID, 0, len(memberships))
+	for _, m := range memberships {
+		if m.Status != MembershipStatusActive {
+			continue
+		}
+		recipients = append(recipients, m.UserID)
+	}
+	if len(recipients) == 0 {
+		return
+	}
+	intent := LobbyNotification{
+		Kind:           NotificationGamePaused,
+		IdempotencyKey: fmt.Sprintf("paused:%s:%d", gameID, turn),
+		Recipients:     recipients,
+		Payload: map[string]any{
+			"game_id": gameID.String(),
+			"turn":    turn,
+			"reason":  reason,
+		},
+	}
+	if pubErr := s.deps.Notification.PublishLobbyEvent(ctx, intent); pubErr != nil {
+		s.deps.Logger.Warn("game-paused notification failed",
+			zap.String("game_id", gameID.String()),
+			zap.Int32("turn", turn),
+			zap.Error(pubErr))
+	}
+}
+
 // OnGameFinished completes the game lifecycle: marks the game as
 // `finished`, evaluates capable-finish per active member, and
 // transitions reservation rows to either `pending_registration`
@@ -278,13 +335,28 @@ func mergeRuntimeSnapshot(prev, next RuntimeSnapshot) RuntimeSnapshot {
 // nextStatusFromSnapshot maps the runtime-reported runtime status into
 // a lobby status transition. Returns (next, true) when the lobby
 // status must change; (current, false) otherwise.
+//
+// The map intentionally distinguishes the pre-running boot path
+// (`starting → start_failed`) from the in-flight failure path
+// (`running → paused`). Paused games can be resumed by the admin via
+// the explicit `/resume` transition; the runtime keeps the engine
+// container alive, the scheduler short-circuits ticks while paused,
+// and any user-games command/order is rejected by the order handler
+// with `turn_already_closed` until the game resumes.
 func nextStatusFromSnapshot(currentStatus string, snapshot RuntimeSnapshot) (string, bool) {
 	switch snapshot.RuntimeStatus {
 	case "running":
 		if currentStatus == GameStatusStarting {
 			return GameStatusRunning, true
 		}
-	case "engine_unreachable", "start_failed", "generation_failed":
+	case "engine_unreachable", "generation_failed":
+		if currentStatus == GameStatusStarting {
+			return GameStatusStartFailed, true
+		}
+		if currentStatus == GameStatusRunning {
+			return GameStatusPaused, true
+		}
+	case "start_failed":
 		if currentStatus == GameStatusStarting {
 			return GameStatusStartFailed, true
 		}