Implement rig animation controls in the test harness

- Added a new animation specification document for Phase 9 Task 5 detailing the requirements for rig animation controls.
- Introduced a new `StickmanRig` script to manage the facing direction and joint bending for the rig.
- Implemented UI elements in the test harness for selecting animations, controlling playback (play/pause/resume/stop), and toggling loop mode.
- Enhanced the `test_harness.gd` script to handle animation playback state and UI interactions.
- Updated documentation in `AGENTS.md`, `README.md`, and `RIGGING.md` to reflect the new animation features.

RIGGING.md

@@ -98,5 +98,21 @@ The display should be easy to read to the right side of the screen. There should
 
 ## Task 4: Refactor facing direction / bone bend
 
+**Implemented (Phase 9 Task 4)** — see `docs/phase9_task4_refactor_spec.md`; a new
+`scripts/stickman_rig.gd` (`class_name StickmanRig`, attached to the `master_rig.tscn` root)
+now owns the facing preset, the four per-joint TwoBoneIK bend flags, and the `Body/*` z-order
+as exported controls; the test harness became a thin driver that reads/writes the rig script.
+
 We need to have facing direction and bone bend to be a part of the master_rig.tscn. This rig will be used for instances of stickmen which will be able to face different directions / have different bone bending at a time.
 So rather than keeping that data in the harness, we need it in the master rig. These should probably be exported controls too so that they can easily be accessed.
+
+## Task 5: Rig animation
+
+**Implemented (Phase 9 Task 5)** — see `docs/phase9_task5_animation_spec.md`; the harness adds a dropdown, play/pause/resume, stop, and loop controls that drive the rig's `AnimationPlayer` directly.
+
+Both AnimationPlayer and AnimationTree has been added to the master_rig.tscn. Animations should be selectable and playable in the harness.
+
+- Default animations are inside the AnimationPlayer: currently just 'walk_right'
+- There should be a dropdown in the harness where the user can select an animation.
+- There should also be a play/pause/stop button that will start the animation, pause/resume, or stop (animation will restart on play)
+- there should be a button that toggles if the animation will loop or play just once.