feat: expand progression and multiplayer systems

Add named save slots, progression import/export, and a unified play flow. Add live friend requests, presence, invitations, and relationship controls without durable discovery-server social storage. Advance the network protocol with isolated channels, movement reconciliation, late-join recovery, fishing replication, and animation synchronization. Preserve per-species catch totals, refine generated-world startup and water recovery, and complete the related input and interface improvements.

tests/light_performance_profile_validation.gd

@@ -24,6 +24,12 @@ func _run() -> void:
 	for _frame: int in 8:
 		await process_frame
 	assert(bool(main.get("_application_initialized")))
+	assert(bool(main.call(
+		"_apply_world",
+		WorldLayout.GENERATED,
+		PlayerSaveManager.DEFAULT_WORLD_SEED,
+		true,
+	)))
 	_validate_main_profile(main)
 	_validate_minimal_weather(main)
 	_stop_audio_players(main)
@@ -42,6 +48,12 @@ func _run() -> void:
 	for _frame: int in 8:
 		await process_frame
 	assert(bool(normal_main.get("_application_initialized")))
+	assert(bool(normal_main.call(
+		"_apply_world",
+		WorldLayout.GENERATED,
+		PlayerSaveManager.DEFAULT_WORLD_SEED,
+		true,
+	)))
 	_validate_normal_profile(normal_main)
 	_validate_new_game_music_transition(normal_main)
 	_stop_audio_players(normal_main)