Completes the TS-3 stub (the deferred 'full physics port'):
- ValidateTransition: the fsf increment/reset ladder + the fsf>=3 upward-contact-plane
manufacture (retail validate_transition 0x0050aa70 pc:272625-656; ACE Transition.cs:
1029-1061). Runs after acdream's fused contact block (structural adaptation preserving
the L.2.3c/L.2.4/A6.P3 contact-retention divergences), deriving retail's _redo as
cleanAdvance || OnWalkable — a grounded wall-slide is not a stuck-fall.
- The sweep-loop fsf early-out (retail find_valid_position pc:273745 / ACE :587): stop
as soon as fsf != 0, so a later advancing sub-step can't reset it in the same frame
(load-bearing — without it the counter never escalates across frames).
- ObjectInfo.MoverHasGravity gate (pc:272625).
- PhysicsEngine: seed ci.fsf from the body's Stationary* bits AFTER InitPath
(retail transition() pc:280940-947); writeback publishes body.FramesStationaryFall +
encodes the Stationary* bits (co-located with the fsf compute so the round-trip is
self-contained in Core; retail encodes in handle_all_collisions — register note).
Tests: FramesStationaryFallTests — an airborne jump wedged under an overhead creature
escalates fsf 0->1->2->3 and at fsf 3 manufactures the UP plane (grounded 'glide onto
the crowd top'); a grounded wall-slide never accumulates fsf. Core 2609/0.
Behaviour dormant in ordinary locomotion (fsf stays 0 unless a gravity mover is blocked).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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