Six-task plan for Bug A slice (spec 2026-05-20):
1. Replace synthesis call site with return TransitionState.OK
2. Delete Transition.TryFindIndoorWalkablePlane method + constant
3. Delete IndoorWalkablePlaneTests.cs + TransitionTypesTests.cs
4. Run physics suite, confirm baseline holds
5. Single commit per spec
6. User visual verification (5 scenarios)
Net delta: ~-480 lines. BSPQuery.FindWalkableSphere + its 5 unit tests
retained as the underlying retail-faithful walkable-finder API.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
