fix(movement+anim+session): clothing dedup, motion wire format, jump-skill default

Three separate fixes landed today, each addressing a specific bug the
user observed during live play:

1. NPC clothing changes by camera angle (InstancedMeshRenderer)
   - Group key was (GfxObjId) only, so every humanoid NPC using the
     same body mesh piled into one instance group; only the first
     instance's texture was used for the entire DrawInstanced batch,
     so which NPC's palette "won" changed as frustum culling and
     iteration order shuffled entries.
   - Now keyed by (GfxObjId, PaletteHash ^ SurfaceOverridesHash)
     so only compatible instances batch; each unique appearance gets
     its own draw call. Perf hit is small (humanoid NPCs each emit
     one more draw call); visually every NPC is now stable.

2. GpuWorldState dedup on respawn
   - Server re-sends CreateObject for the same guid on visibility
     refresh / landblock crossing / appearance update. AppendLiveEntity
     was blindly appending each time, so GpuWorldState accumulated
     multiple copies of the same entity, each with its own
     PaletteOverride / MeshRefs. That alone wasn't the clothing bug
     (that was #1) but it would have caused other overlap problems
     downstream.
   - Added RemoveEntityByServerGuid + WorldGameState.RemoveById;
     OnLiveEntitySpawnedLocked calls both before creating the new
     entity so respawns replace cleanly.

3. Motion wire format — run animation sync with retail observers
   - ACE's MovementData constructor only computes interpState.ForwardSpeed
     on the WalkForward/WalkBackwards branch; every other ForwardCommand
     falls into `else` and passes through WITHOUT speed set, giving
     observers speed=0. Sending RunForward directly meant retail
     clients saw us "run in place" while position drifted forward.
   - Wire: always WalkForward + HoldKey.Run for running. ACE
     auto-upgrades to RunForward with creature.GetRunRate() for
     broadcast — correct command + correct speed at observers.
   - Added per-axis FORWARD_HOLD_KEY / SIDE_STEP_HOLD_KEY /
     TURN_HOLD_KEY so every active axis carries HoldKey.Run when
     running (matches holtburger's build_motion_state_raw_motion_state).
   - Added LocalAnimationCommand to MovementResult so our own
     client still plays the RunForward cycle locally while the wire
     stays WalkForward. Wire vs. local animation command are now
     decoupled.
   - Walk-backward wire command changed from WalkForward@-0.65 to
     WalkBackward@1.0 (holtburger pattern).
   - Strafe speed changed from 0.5 to 1.0 on wire AND local physics
     (matches retail sidestep pace).

4. Jump height default + env-var tuning
   - Default jumpSkill bumped from 100 → 200 (jump ≈ 3m at full
     charge, closer to retail feel for a mid-level character).
   - ACDREAM_RUN_SKILL and ACDREAM_JUMP_SKILL env vars now override
     the defaults so the user can tune per-character until we parse
     PlayerDescription and plumb real skill values through.

5. JustLanded signal on MovementResult
   - Tracks airborne→grounded transition so future animation code
     can fire the landing cycle when we land. Just a bool flag for
     now — no consumer yet (the proper action-queue path will use it).

Not in this commit: jump animation itself. An earlier attempt to
SetCycle(Jump=0x2500003b) fed an Action-type motion into the SubState
cycle resolver, which produced a "torso" mis-render. Reverted. The
proper fix is porting the retail motion action-queue semantics into
AnimationSequencer — see docs/research/deepdives/r03-motion-animation.md
for the spec. That's the next session's work.

470 tests pass, build clean.

src/AcDream.Core/Plugins/WorldGameState.cs

@@ -11,4 +11,12 @@ public sealed class WorldGameState : IGameState
 
     /// <summary>Called by the host as each entity is hydrated.</summary>
     public void Add(WorldEntitySnapshot snapshot) => _entities.Add(snapshot);
+
+    /// <summary>
+    /// Remove any snapshot with the given local <c>Id</c>. Used when the
+    /// server re-sends <c>CreateObject</c> for an entity already known to
+    /// acdream — the host deletes the old snapshot before adding the new
+    /// one so plugins don't see stale duplicates.
+    /// </summary>
+    public void RemoveById(uint id) => _entities.RemoveAll(e => e.Id == id);
 }