fix(client): address PR #70 review — event leak, quit flush, notification color

- input_mapper.gd: call set_input_as_handled() before early return on
  empty game_id so F5/F6 events don't propagate to other handlers
- session_manager.gd: defer scene change by one frame after buffering
  quit-save so SimBridge._process() flushes the outbound buffer
- monologue_display.gd: tag queued notifications with is_notification
  flag so drain path routes to _show_notification_line (correct color)
  instead of _show_line (lattice-profile fallback color)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/ui/monologue_display.gd

@@ -64,7 +64,10 @@ func _process(delta: float) -> void:
 		var now := float(Time.get_ticks_msec())
 		if now >= _next_fade_in_msec:
 			var next: Dictionary = _queue.pop_front()
-			_show_line(next.text, next.duration, next.priority, next.is_urgent, next.lattice_profile)
+			if next.get("is_notification", false):
+				_show_notification_line(next.text)
+			else:
+				_show_line(next.text, next.duration, next.priority, next.is_urgent, next.lattice_profile)
 
 
 # Display a monologue line.
@@ -82,7 +85,15 @@ func show_notification(text: String) -> void:
 	if _visible.size() < MAX_VISIBLE and now >= _next_fade_in_msec:
 		_show_notification_line(text)
 	else:
-		_enqueue(text, _NOTIFICATION_DURATION, 1, false, "")
+		var entry := {text = text, duration = _NOTIFICATION_DURATION, priority = 1, is_urgent = false, lattice_profile = "", is_notification = true}
+		if _queue.size() < MAX_QUEUE:
+			_queue.append(entry)
+			_queue.sort_custom(func(a: Dictionary, b: Dictionary) -> bool: return a.priority > b.priority)
+		else:
+			var lowest := _lowest_priority_idx()
+			if 1 >= _queue[lowest].priority:
+				_queue[lowest] = entry
+				_queue.sort_custom(func(a: Dictionary, b: Dictionary) -> bool: return a.priority > b.priority)
 
 
 func show_monologue(text: String, duration: float, priority: int = 2, is_urgent: bool = false) -> void: