Implement playable Mac client and rendering validation

project/app_flow_lifecycle_test.gd

@@ -48,6 +48,9 @@ func _init() -> void:
 			"AppLifecycle survives login screen construction")
 	_ck(client.get_parent() == flow,
 			"AppFlow keeps the same client beside lifecycle coordinator")
+	var login_snapshot: Dictionary = flow.get_playable_snapshot()
+	_ck(login_snapshot.get("stage", "") == "LOGIN" and not login_snapshot.get("scene_ready", true),
+			"playable snapshot is a read-only LOGIN summary")
 
 	# A live game keeps its scene during a transient disconnect. ReconnectUI
 	# owns the retry while the next character list silently re-enters the last
@@ -67,6 +70,9 @@ func _init() -> void:
 	_ck(flow.state() == AppFlow.GAME and not flow._reconnecting_game
 			and not flow._reconnect.is_showing(),
 			"successful reconnect restores GAME and hides overlay")
+	var game_snapshot: Dictionary = flow.get_playable_snapshot()
+	_ck(game_snapshot.get("stage", "") == "GAME" and not game_snapshot.get("reconnecting", true),
+			"playable snapshot reports GAME after reconnect")
 
 	flow.queue_free()
 	await process_frame