fix(anim): jump animation via Falling SubState + kept PlayAction infra for emotes

The actual retail behavior for jump animations is a plain SubState swap —
NOT an Action overlay as I'd initially guessed. MotionCommand.Falling
(0x40000015) is a SubState cycle whose motion-table entries handle the
whole jump lifecycle:

  - Links[(stance, RunForward)][Falling]     = leap-into-air link
  - Cycles[(stance, Falling)]                = airborne cycle (loops)
  - Links[(stance, Falling)][Ready/...]      = landing link back to normal

Empirical verification from the diagnostic dump:
    Links[0x003D0007] has 3 inner entries:
        inner key: 0x41000003 (Ready)
        inner key: 0x45000005 (WalkForward)
        inner key: 0x40000015 (Falling) ← jackpot

SetCycle() already handles SubState + Links + Cycles resolution correctly,
so the whole fix is three lines:

    if (!result.IsOnGround)
        animCommand = MotionCommand.Falling;

What's in this commit:
- Added MotionCommand.Falling (0x40000015) constant + comments explaining
  the retail jump-is-a-SubState flow
- GameWindow.UpdatePlayerAnimation swaps to Falling when airborne (the
  cleanest possible implementation — motion table does all the work)
- Kept AnimationSequencer.PlayAction infrastructure (ported via Links
  fallback + Modifiers fallback). Not needed for jump, but perfectly
  valid for emotes like /wave, /bow (found in the same Links dict as
  inner keys 0x13000080-0x13000083) and eventual combat attacks
- Kept MotionCommand.Jump / Jumpup / FallDown constants (unused for now
  but useful reference if non-humanoid motion tables use them)
- Removed all diagnostic logging

What was learned (for future motion work):
- Retail's MotionTable.Cycles dict holds SubState loops (Ready, Walk,
  Run, Falling, Crouch, etc.) by (style<<16) | (motion & 0xFFFFFF)
- MotionTable.Links dict holds TRANSITIONS between motions: the OUTER
  key is the (style, fromMotion) combo; the INNER key is the TARGET
  motion. The stored MotionData IS the link animation played during
  the transition. This is what ACE's get_link traverses.
- MotionTable.Modifiers dict holds overlay motions (mask 0x20) — rare
  for humanoids, only 8 TurnRight/SideStepRight stance variants
- Actions (mask 0x10) in retail ALSO go through Links — they're
  transition animations FROM current substate, not overlays. Use
  PlayAction (now correctly routed to Links dict) for them.

Jump animation now works retail-faithfully for running + jumping off.
Standing-jump behavior depends on whether the player's motion table
has a Ready→Falling link; SetCycle's fallback chain should handle it
via the style-level catch-all if the direct link is absent.

470 tests pass. Build clean.

src/AcDream.App/Rendering/GameWindow.cs

@@ -3037,46 +3037,30 @@ public sealed class GameWindow : IDisposable
     {
         if (_dats is null) return;
 
-        // ── Action-motion events (jump / land) ─────────────────────────────
+        // ── Airborne SubState (Falling) ────────────────────────────────────
         //
-        // Retail does NOT animate jumps — confirmed via ACE's HandleActionJump
-        // (Player.cs:914-915) which explicitly clears PendingMotions and
-        // sets IsAnimating=false during the jump. The character keeps
-        // whatever cycle it was on and the physics body arcs through the air.
-        // Humanoid Setup MotionTables have NO entry for Jump (0x2500003B)
-        // or FallDown (0x10000050) in the Modifiers dict — verified empirically
-        // (only 8 TurnRight stance-variants + SideStepRight).
+        // Retail models the jump-animation as a SubState swap to
+        // MotionCommand.Falling (0x40000015) while airborne, NOT as an
+        // Action overlay. Empirically verified: Links[(NonCombat,RunForward)]
+        // has 3 transitions including 0x40000015 Falling. The SubState cycle
+        // for Falling lives in Cycles[(style, Falling)] and loops while
+        // airborne. On land, we transition back to whatever SubState the
+        // motion input implies (Ready / WalkForward / RunForward).
         //
-        // We still call PlayAction here as a no-op safety hatch: if a future
-        // Setup / creature DOES carry a jump/fall modifier in its MotionTable
-        // (e.g. a leaping-monster) the sequencer will pick it up for free.
-        // For player humanoids, the lookup silently misses and nothing changes.
-        if (result.JumpExtent.HasValue || result.JustLanded)
-        {
-            if (_entitiesByServerGuid.TryGetValue(_playerServerGuid, out var actionPe)
-                && _animatedEntities.TryGetValue(actionPe.Id, out var actionAe)
-                && actionAe.Sequencer is not null)
-            {
-                if (result.JumpExtent.HasValue)
-                    actionAe.Sequencer.PlayAction(AcDream.Core.Physics.MotionCommand.Jump);
-                if (result.JustLanded)
-                    actionAe.Sequencer.PlayAction(AcDream.Core.Physics.MotionCommand.FallDown);
-            }
-        }
+        // Implementation: force animCommand = Falling when airborne; the
+        // existing SetCycle pathway resolves the link + cycle correctly and
+        // the transition back happens naturally when airborne becomes false.
 
-        // Determine the animation command: forward takes priority, then sidestep,
-        // then turn, then idle (Ready 0x41000003).
+        // Determine the animation command: airborne takes priority (Falling
+        // SubState), then forward, sidestep, turn, then idle (Ready 0x41000003).
         //
-        // Note: AC's Jump (0x2500003b) is an Action motion (mask 0x25000000),
-        // NOT a SubState cycle. Feeding it to the MotionTable resolver via
-        // SetCycle produces a failed cycle lookup — which mis-renders the
-        // character. Proper action playback needs a separate sequencer path
-        // that honors the motion table's action queue; that's deferred.
-        // For now the player stays in whatever cycle was active when they
-        // jumped (usually walk/run or Ready) — animation wise it's wrong but
-        // at least the character doesn't implode.
+        // Airborne → Falling (retail behavior; see airborne note above).
+        // Otherwise: LocalAnimationCommand (RunForward when running) preferred,
+        // falling back to wire ForwardCommand (WalkForward / WalkBackward).
         uint animCommand;
-        if (result.LocalAnimationCommand is { } localCmd)
+        if (!result.IsOnGround)
+            animCommand = AcDream.Core.Physics.MotionCommand.Falling;
+        else if (result.LocalAnimationCommand is { } localCmd)
             animCommand = localCmd;
         else if (result.ForwardCommand is { } fwd)
             animCommand = fwd;