feat(B.4c): [door-cycle] diagnostic in OnLiveMotionUpdated

Logs one line per UpdateMotion arriving for an entity named "Door"
when ACDREAM_PROBE_BUILDING=1. Greppable trail for the B.4c visual
test: confirms the dispatcher hit the sequencer for door open / close.

Durable subsystem-named tag per the Opus reviewer's B.4b feedback
([B.4c] would rot after phase archival; [door-cycle] survives).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -3149,6 +3149,15 @@ public sealed class GameWindow : IDisposable
                 $"| seq now style=0x{seqStyle:X8} motion=0x{seqMotion:X8}");
         }
 
+        // Phase B.4c — durable per-Door UM dispatch trail for visual-test grep.
+        if (AcDream.Core.Physics.PhysicsDiagnostics.ProbeBuildingEnabled
+            && _liveEntityInfoByGuid.TryGetValue(update.Guid, out var doorInfo)
+            && doorInfo.Name == "Door")
+        {
+            Console.WriteLine(System.FormattableString.Invariant(
+                $"[door-cycle] guid=0x{update.Guid:X8} stance=0x{update.MotionState.Stance:X4} cmd=0x{(update.MotionState.ForwardCommand ?? 0u):X4}"));
+        }
+
         // Wire server-echoed RunRate first — used for the player's own
         // locomotion tuning regardless of whether a cycle resolves.
         if (_playerController is not null