Slice 2 of 2 in the indoor ContactPlane retention phase. Deletes
Transition.TryFindIndoorWalkablePlane + the per-frame synthesis call
+ outdoor-terrain fallthrough + 9 tests. Replaces with bare
return TransitionState.OK; matching retail's BSPTREE::find_collisions
OK path (acclient_2013_pseudo_c.txt:323938). ContactPlane is retained
via the per-tick seed at PhysicsEngine.ResolveWithTransition:583
(init_contact_plane equivalent) or refreshed by BSP Path 3 / Path 4.
Predecessor: de8ffde (Bug B, BSP world-origin fix).
Evidence: launch-cp-probe-postfix-v2.log shows 3150 MISS / 3154
indoor-walkable calls (99.87% miss rate) after Bug B, with user-visible
"stuck falling when brushing upper floor edge" symptom unchanged.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
