Add Cinemachine third-person orbit camera and fix paint raycast

- Install Cinemachine 3.1.7 and set up an orbital third-person camera rig
  (CinemachineBrain, OrbitalFollow, RotationComposer, Deoccluder).
- Add ThirdPersonOrbitInput: mouse-driven orbit and wheel zoom with a Tab
  toggle that unlocks the cursor and pauses rotation.
- Fix MeshPainter so the paint ray skips the player's CharacterController
  capsule (and any other collider) and always targets the mesh collider,
  so painting works from every camera angle.

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

Assets/Scripts/ThirdPersonOrbitInput.cs.meta

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