fix(renderer): drain threaded loads on shutdown

src/tools/capture_render_checkpoints.gd

@@ -2,6 +2,7 @@ extends SceneTree
 
 const DEFAULT_MANIFEST_PATH := "res://src/tools/render_baseline_manifest.json"
 const M2_NATIVE_ANIMATED_BUILDER := preload("res://addons/mpq_extractor/loaders/m2_native_animated_builder.gd")
+const SHUTDOWN_DRAIN_FRAMES := 2
 
 
 func _initialize() -> void:
@@ -167,6 +168,10 @@ func _capture_async() -> void:
 	print("RENDER_BASELINE report=%s results=%d" % [report_path, captured])
 
 	world.queue_free()
+	# SceneTree deletion is deferred. Allow the world and its queued children
+	# to run their shutdown paths before engine teardown.
+	for unused_frame in SHUTDOWN_DRAIN_FRAMES:
+		await process_frame
 	if captured <= 0:
 		push_error("No checkpoints selected. --only filter was: %s" % only)
 		quit(1)