Save The Tree implementation and acceptance work in progress

Preserve production code, regression fixtures, audio assets and provenance, test infrastructure, and the original-completion plan and progress ledger. Final game and Windows acceptance remain pending; excluded local artifacts and native experiments are not part of this snapshot.

tests/ui/test_world_tree_rank.gd

@@ -1,4 +1,5 @@
 extends SceneTree
+const FixtureCleanup := preload("res://tests/helpers/ui_audio_fixture_cleanup.gd")
 var checks:=0
 var failures:=0
 func expect(ok: bool, message: String) -> void:
@@ -85,5 +86,10 @@ func run() -> void:
 	main.call("_load_manual")
 	expect(button.text=="世界樹ランク 2" and runtime.world_service.get_bounds()==ProgressionService.RANK_BOUNDS[2],"normal load restores promoted HUD and map bounds")
 	SaveService.delete_save(save_path)
-	main.queue_free();await process_frame
+	var _audio_cleanup_final: Dictionary = await FixtureCleanup.free_owner_and_wait(self, main)
+	if not bool(_audio_cleanup_final.get(&"passed", false)):
+		push_error("Ordinary fixture audio cleanup failed: %s" % str(_audio_cleanup_final))
+		quit(96)
+		return
+	await process_frame
 	print("World tree rank UI: %d checks, %d failures" % [checks,failures]);quit(failures)