feat: Implement kinematic-to-ragdoll transition system

- Added KINEMATIC_BLENDING_AND_RECOVERY.md to outline features for smooth transitions between kinematic and ragdoll states, including visual and physical blending, and ragdoll recovery.
- Introduced KINEMATIC_TO_RAGDOLL.md detailing the objectives, scope, and core architecture for transitioning the stickman from kinematic to ragdoll mode.
- Created KINEMATIC_TO_RAGDOLL_SPEC.md as an implementation specification, verifying codebase facts and correcting the initial plan based on Godot 4.4 source.
- Enhanced StickmanRig with state management for animated and ragdoll modes, including momentum preservation and ragdoll construction.
- Updated physics_test_harness to support toggling between kinematic and ragdoll states with user input.

.opencode/agents/developer.md

@@ -78,6 +78,16 @@ _Brief 1-2 sentence overview of what the reviewed component does._
 - **Current**: [Describe bottleneck/tight coupling]
 - **Recommendation**: [Describe optimized approach]
 
+### 🔧 Runtime Tech-Debt Discovery
+
+While writing code, if you encounter:
+
+- Ugly workarounds forced by existing code.
+- Performance pitfalls you have to code around.
+- Unused imports, dead code, or outdated comments that are confusing.
+
+**Immediately** append to `docs/tech_debt_and_optimizations.md` with the same format.
+
 ### 🎨 Style & Readability Refactors
 
 - _Bullet points pointing out missing type hints, naming violations, or dead code._