fix(M00): release GUI capture render resources

Work-Package: M00-QAR-GUI-RID-SHUTDOWN-001
Agent: sindo-main-codex
Tests: render baseline dry-run; runtime cache shutdown; comparator self-test; coordination and documentation gates
Fidelity: shutdown-only ownership fix; no visual or Blizzlike335 behavior change

addons/mpq_extractor/loaders/adt_builder.gd

@@ -788,7 +788,10 @@ static func _build_tile_water_root(data: Dictionary, origin_offset: Vector3) ->
 		mi.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
 		root.add_child(mi)
 
-	return root if root.get_child_count() > 0 else null
+	if root.get_child_count() > 0:
+		return root
+	root.free()
+	return null
 
 
 static func _append_liquid_geometry(