Import Opsive UCC in an isolated Unity pass

[JOY]

Project: Second Spawn
Area: Unity
Milestone: Vertical Slice
Priority: P1
Size: L
Review Gate: Local Review
Verification: Unity Smoke

Goal

Import Opsive Ultimate Character Controller in its own branch and commit, then evaluate whether it should replace, augment, or stay deferred behind the current Simple KCC controller.

Acceptance Criteria

• Asset import happens in an isolated change set.
• Unity console is checked after import.
• Compatibility notes are added to docs/setup/agent-handoff.md or a dedicated evaluation note.
• No controller replacement happens until the evaluation result is documented.