feat(R3-W4): ground transitions + lifecycle verbatim; K-fix18 DELETED (closes J8, J10, J11-shape, J12, J13, J18, J19)

Core (dedicated agent, independently reviewed): HitGround 0x00528ac0 /
LeaveGround 0x00528b00 verbatim (creature+gravity gates, the
RemoveLinkAnimations seam — K-fix18's retail mechanism — velocity via
GetLeaveGroundVelocity with the autonomous flag, jump-state resets,
apply_current_movement re-sync); enter_default_state 0x00528c80 per A8
(fresh states, InitializeMotionTables seam, sentinel APPENDED without
draining pending_motions — pinned, Initted=1, LeaveGround tail);
Initted gates; the A3 IsThePlayer dual dispatch in
apply_current_movement / ReportExhaustion / SetWeenieObject /
SetPhysicsObject (a remote player routes INTERPRETED — the
ACE-divergence pin); set_hold_run 0x00528b70 + SetHoldKey 0x00528bb0
(XOR guard, None-only-from-Run); adjust_motion creature guard wired
(TS-34 retired); PhysicsBody.LastMoveWasAutonomous +
set_local_velocity(autonomous). Port discovery: retail's
apply_raw_movement 0x005287e0 / apply_interpreted_movement 0x00528600
ARE the already-shipped D6.2a/funnel functions — the dual dispatch
composes them instead of duplicating.

App cutover (orchestrator): the skipTransitionLink flag + both K-fix18
call sites DELETED (AP-74 retired). MotionInterpreter.DefaultSink routes
apply_current_movement's interpreted branch through the REAL funnel
dispatch when a sink is bound — so a remote's LeaveGround engages
Falling via the contact-gated funnel, replacing the forced SetCycle
(J19); the per-remote MotionTableDispatchSink is now PERSISTENT
(EnsureRemoteMotionBindings: DefaultSink + RemoveLinkAnimations +
InitializeMotionTables seams, idempotent from both the UM and
VectorUpdate paths; wire velocity re-applied after LeaveGround so it
stays authoritative). Player: seams bound to the player sequencer; the
controller's grounded→airborne EDGE now fires LeaveGround (jump()
clears OnWalkable and the same frame's transition detection fires it —
retail's order; walk-off-a-ledge gets the momentum fallback + link
strip it never had); the manual jump-block LeaveGround deleted;
LastMoveWasAutonomous set at the controller chokepoint (W6 refines).

Trace S8 re-expressed as the retail mechanism (Falling dispatch +
RemoveAllLinkAnimations = same final state the flag produced). 43 new
lifecycle tests. Registers: TS-34 + AP-74 retired; TS-38, AP-77, AP-78
added. Full suite: 3,665 passed. Live smoke: in-world clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/AcDream.Core/Physics/AnimationSequencer.cs

@@ -40,7 +40,7 @@ public sealed class DatCollectionLoader : IAnimationLoader
 // see CSequence.cs/AnimSequenceNode.cs/FrameOps.cs). This adapter keeps every
 // public member's signature (the API-migration table in the gap map is the
 // contract) and re-expresses each one over the core. Invented mechanisms that
-// are still R2/R3 scope (K-fix18 skipTransitionLink, Fix B locomotion
+// were R2/R3 scope (K-fix18 skipTransitionLink DELETED in R3-W4, Fix B locomotion
 // link-skip, stop-anim fallback, GetLink's reversed branch, velocity/omega
 // synthesis constants) SURVIVE unchanged at the adapter level per the gap
 // map's "Invented behaviors NOT in the gap list" note.
@@ -339,15 +339,7 @@ public sealed class AnimationSequencer
     /// <param name="style">MotionCommand style / stance (e.g. NonCombat 0x003D0000).</param>
     /// <param name="motion">Target motion command (e.g. WalkForward 0x45000005).</param>
     /// <param name="speedMod">Speed multiplier applied to framerates (1.0 = normal).</param>
-    /// <param name="skipTransitionLink">K-fix18 (2026-04-26): when true, do
-    /// NOT enqueue the transition-link frames between the previous and
-    /// new cycle. Used when the caller wants the new cycle to engage
-    /// instantly — e.g. swapping to Falling on a jump start, where the
-    /// RunForward→Falling link is a short "stop running" pose that
-    /// makes the jump look delayed (legs stand still for ~100 ms while
-    /// the link drains, then fold into Falling). Defaults to false to
-    /// preserve normal smooth transitions for everything else.</param>
-    public void SetCycle(uint style, uint motion, float speedMod = 1f, bool skipTransitionLink = false)
+    public void SetCycle(uint style, uint motion, float speedMod = 1f)
     {
         EnsureInitialized();
 
@@ -394,17 +386,11 @@ public sealed class AnimationSequencer
         uint dispatchResult = PerformMovement(
             MotionTableMovement.Interpreted(adjustedMotion, adjustedSpeed));
 
-        // K-fix18 (2026-04-26, register row survives → R3): instant-engage
-        // cases (Falling on jump start) strip the just-selected transition
-        // links so the new cycle starts immediately. Post-Q4 expression:
-        // the retail primitive CPhysicsObj::RemoveLinkAnimations
-        // (0x0050fe20 → CSequence::remove_all_link_animations) — exactly
-        // what R3-W4's LeaveGround will call, at which point this flag and
-        // its GameWindow call sites are deleted. The pending-queue entry's
-        // tick count intentionally stays (retail's RemoveLinkAnimations
-        // does not touch the manager queue; the countdown chain absorbs it).
-        if (skipTransitionLink)
-            _core.RemoveAllLinkAnimations();
+        // R3-W4: the K-fix18 skipTransitionLink flag is DELETED — the
+        // instant-Falling engage is now retail's own mechanism: the entity's
+        // MotionInterpreter.LeaveGround (0x00528b00) fires the
+        // RemoveLinkAnimations seam (bound to this sequencer's
+        // RemoveAllLinkAnimations) when the body leaves the ground.
 
         // Failed dispatch (missing cycle for this style, is_allowed reject):
         // retail leaves sequence AND state untouched — no synthesis either.
@@ -446,6 +432,18 @@ public sealed class AnimationSequencer
         }
     }
 
+    /// <summary>
+    /// R3-W4: the retail link-strip primitive
+    /// (<c>CPhysicsObj::RemoveLinkAnimations</c> 0x0050fe20 →
+    /// <c>CSequence::remove_all_link_animations</c> 0x00524ca0). The App
+    /// binds the entity's <c>MotionInterpreter.RemoveLinkAnimations</c> seam
+    /// here so HitGround/LeaveGround strip pending transition links exactly
+    /// where retail does. The pending-queue tick counts intentionally stay
+    /// (retail's primitive does not touch the manager queue; the countdown
+    /// chain absorbs it).
+    /// </summary>
+    public void RemoveAllLinkAnimations() => _core.RemoveAllLinkAnimations();
+
     /// <summary>
     /// R2-Q5: run retail's <c>enter_default_state</c> analog now if it
     /// hasn't run yet (idempotent). Spawn paths call this so an entity with