fix #270: retry spawn placement until first success (lost-cell recovery analog) + attributed probes

The creation-only spawn placement could no-op or fail during the login
flood (cell id not yet hydrated / streaming collision not resident) with
nothing retrying - monsters created in that window stayed
airborne-flagged forever and their action animations remained refused.
Retail's answer to 'object addressed before its cell exists' is the
CObjectMaint lost-cell list (GotoLostCell): park, re-place when the cell
is available. The UM dispatch path now retries SeedRemoteSpawnPlacement
while the body has never been successfully placed (no contact AND no
stored plane); one success ends the retries.

Probes: [SPAWN-PLACE] logs each placement outcome (guid/cell/ok/
contact/walkable); [UM-ACT]/[MT-FAIL] now carry the owning guid via
MotionInterpreter.DiagnosticGuid (probe-identity-attribution lesson)
plus the body's live contact/walkable flags.

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

src/AcDream.App/Physics/LiveEntityMotionRuntimeController.cs

@@ -45,6 +45,8 @@ internal sealed class LiveEntityMotionRuntimeController
             rm.Sink = new AcDream.Core.Physics.Motion.MotionTableDispatchSink(sequencer);
             rm.Motion.DefaultSink = rm.Sink;
         }
+        // #270 probe identity — strip with the probes.
+        rm.Motion.DiagnosticGuid = serverGuid;
         // #174 (2026-07-05): the RemoveLinkAnimations seam is retail
         // CPhysicsObj::RemoveLinkAnimations 0x0050fe20 — a TAILCALL to
         // CPartArray::HandleEnterWorld 0x00517d70 →