Add surface-cluster collider baker for concealment volumes

Generate multiple convex collider proxies from a mesh by growing
triangles into thin slabs (PCA minor-axis thickness gate) and hulling
each slab, so shelves and open compartments stay hollow while boards
count as embedding surfaces. Baked meshes get readable, deterministic
asset names (scene/prefab path + hierarchy + collision index) instead
of GUIDs. ConcealmentMeter now also excludes a furniture's own concave
mesh collider when a ConcealmentColliderBaker sits in its parent,
symmetric to the existing ConcealmentVolume rule.

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

Assets/Scripts/ConcealmentColliderBaker.cs.meta

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