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/stickman_factory.gd

@@ -3,7 +3,7 @@ extends RefCounted
 ## StickmanFactory - Runtime factory for spawning rig instances from .stk files
 ## (Phase 9).
 ##
-## Loads a versioned .stk JSON dictionary and instantiates a master_rig.tscn,
+## Loads a versioned .stk JSON dictionary and instantiates scenes/stickman_rig.tscn,
 ## adapting it via StkRigAdapter. Consumed by the standalone test harness, not
 ## referenced by the editor.
 
@@ -11,7 +11,7 @@ extends RefCounted
 # Constants
 # ---------------------------------------------------------------------------
 
-const RIG_SCENE := preload("res://master_rig.tscn")
+const RIG_SCENE := preload("res://scenes/stickman_rig.tscn")
 
 # ---------------------------------------------------------------------------
 # Public API