Add concealment meter and skinned collider baker; reorganize assets

- ConcealmentMeter: standalone component measuring the percentage of the
  character volume embedded inside environment geometry (bake -> voxelize via
  column ray-stabbing parity -> classify interior voxels against box/sphere/
  capsule/convex colliders and terrain). Always-on, throttled, gizmo debug.
- SkinnedColliderBaker: sole per-frame collider bake owner for skinned rigs.
  MeshPainter now delegates baking and only borrows BakedMesh for the GPU
  raster and cache refresh, so the collider stays fresh outside paint mode.
- Move pose assets to Assets/Poses, retire unused Insect scripts to
  Assets/Unused, restore Paintman.controller; mode scripts and scene updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/MeshPainter.cs

@@ -195,6 +195,9 @@ public partial class MeshPainter : MonoBehaviour
     private SkinnedMeshRenderer _skinned;
     private MeshCollider _collider;
     private Mesh _bakedMesh;
+    // When present, this always-on baker owns the collider bake (also outside paint mode); we
+    // stop baking and only borrow its mesh. Null = no baker -> we keep our own legacy bake.
+    private SkinnedColliderBaker _baker;
     private Material _materialInstance;
 
     // Mesh caches (in local/collider space).
@@ -854,7 +857,7 @@ public partial class MeshPainter : MonoBehaviour
         // scene unload that does not raise OnApplicationQuit; the once-guard prevents a re-save.
         SavePaintOnTeardown();
 
-        if (_bakedMesh) Destroy(_bakedMesh);
+        if (_bakedMesh && !_baker) Destroy(_bakedMesh); // _baker owns its mesh; only free our own
         if (_materialInstance) Destroy(_materialInstance);
         if (_proceduralMask) Destroy(_proceduralMask);
         if (_previewMat) Destroy(_previewMat);