Implement Phase 8: Rig Relocation and Component Modularization

- Moved the rig scene from `res://master_rig.tscn` to `res://scenes/stickman_rig.tscn`, preserving its UID.
- Split the `StickmanRig` controller into three components: `StickmanLocomotion`, `StickmanRagdoll`, and `StickmanActionRunner`.
- Updated the architecture to ensure `StickmanRig` acts as the public facade for the new components.
- Created a new test suite `test_phase8_rig_modularization.gd` to verify the integrity of the relocated rig and its components.
- Added checks for scene loading, component resolution, action queue delegation, and state authority.

scripts/sandbox_stage.gd

@@ -2803,17 +2803,17 @@ func _action_hint_text() -> String:
 func _action_origin() -> Vector2:
 	if _pending_walk_target:
 		if _context_rig != null and is_instance_valid(_context_rig):
-			return _context_rig.global_position - STICKMAN_RIG.FOOT_OFFSET
+			return _context_rig.global_position - StickmanLocomotion.FOOT_OFFSET
 		return Vector2.ZERO
 	if _capture_kind != CaptureKind.NONE:
 		if _walk_edit_rig != null and is_instance_valid(_walk_edit_rig):
-			return _walk_edit_rig.global_position - STICKMAN_RIG.FOOT_OFFSET
+			return _walk_edit_rig.global_position - StickmanLocomotion.FOOT_OFFSET
 		if _panel_rig != null and is_instance_valid(_panel_rig):
-			return _panel_rig.global_position - STICKMAN_RIG.FOOT_OFFSET
+			return _panel_rig.global_position - StickmanLocomotion.FOOT_OFFSET
 		return Vector2.ZERO
 	if _rule_step != RuleStep.IDLE:
 		if _rule_context_rig != null and is_instance_valid(_rule_context_rig):
-			return _rule_context_rig.global_position - STICKMAN_RIG.FOOT_OFFSET
+			return _rule_context_rig.global_position - StickmanLocomotion.FOOT_OFFSET
 		var trigger: Dictionary = _rule_builder.get("trigger", {})
 		var src := instance_from_id(int(trigger.get("source", -1)))
 		if src is Node2D and is_instance_valid(src):
@@ -3467,7 +3467,7 @@ func _update_area_entry() -> void:
 ## Stickman point = feet (root - FOOT_OFFSET); prop point = global position.
 func _movable_point(node: Node2D) -> Vector2:
 	if node is STICKMAN_RIG:
-		return node.global_position - StickmanRig.FOOT_OFFSET
+		return node.global_position - StickmanLocomotion.FOOT_OFFSET
 	return node.global_position
 
 
@@ -3636,7 +3636,7 @@ func _begin_walk_edit(rig: StickmanRig, index: int, from_panel: bool) -> void:
 	_walk_edit_index = index
 	_walk_edit_from_panel = from_panel
 	var queue := rig.get_queue()
-	var pos: Vector2 = queue[index].get("target", rig.global_position - STICKMAN_RIG.FOOT_OFFSET)
+	var pos: Vector2 = queue[index].get("target", rig.global_position - StickmanLocomotion.FOOT_OFFSET)
 	_director_visuals.set_edit_waypoint(pos)
 	_begin_capture(CaptureKind.POSITION, "🚩 Click the new waypoint position (Esc or RMB to cancel)", _on_walk_edit_captured, _cb_walk_edit_cancel)