Add Phase 4 Final Bugs Specification and Tests

- Introduced a new architecture specification for Phase 4 final bugs, detailing scope, decisions, runtime data contracts, action roles, execution lanes, speech ownership, and signal flow.
- Implemented changes in `scripts/action_registry.gd`, `scripts/action_editor.gd`, `scripts/sandbox_stage.gd`, `scripts/stage_gizmos.gd`, `scripts/stickman_factory.gd`, and `scripts/stickman_rig.gd` to address identified bugs.
- Created a new test suite `tests/test_phase4_final_bugs.gd` to validate the implementation, covering action roles, grid snapping, prop manipulation, reactive runtime lane, spawn pose preservation, and more.
- Added a unique identifier for the test file to ensure proper tracking and management.

scripts/stickman_factory.gd

@@ -37,6 +37,7 @@ static func load_stk(path: String) -> Dictionary:
 static func spawn_from_data(stk_data: Dictionary) -> StickmanRig:
 	var rig := RIG_SCENE.instantiate() as StickmanRig
 	StkRigAdapter.apply(stk_data, rig)
+	rig.initialize_spawn_pose_from_skeleton()
 	return rig