probe(render): cathedral Phase I instrumentation

Implements the synthesis plan''s Phase I (instrument-first, no rendering
edits): the [falls] watch printing EVERY particle submission carrying a
real falls owner (the outdoor landblock emitters 0xCF418000-13 the six
fix rounds never traced) with route + phase; [falls-adm] admission
verdicts for F418 emitters at the retail ShouldDrawParticles port
(owner, cell, distance, in-set, eligibility); the continuous
[walk-root] line now separating the TRUE root flood
(InteriorFloodCells) from the visited union (root + look-ins - the
conflation the review corpus indicted) and printing the walk''s own
exit-view count; [walk-cam] replayable camera dumps; and the restored
[walk-portal] per-portal side/clip decisions. All under the existing
ACDREAM_PROBE_WALK_ROOT flag; the depth-checkpoint readback is
deferred until these answers narrow the question (mid-pass Vulkan
depth reads need render-pass splitting).

Hermetic 6,762/0.

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

src/AcDream.Core/Vfx/ParticleSystem.cs

@@ -321,6 +321,9 @@ public sealed class ParticleSystem : IParticleSystem
             rangeMultiplier = 1f;
 
         LastRetailViewEmitterVisitCount = 0;
+        _probeAdmissionDumpThisCall =
+            AcDream.Core.Rendering.RenderingDiagnostics.ProbeWalkRootEnabled
+            && ++_probeAdmissionCallCounter % 120 == 0;
         foreach (int handle in _worldSimulationHandles)
         {
             if (!_byHandle.TryGetValue(handle, out ParticleEmitter? emitter))
@@ -346,9 +349,33 @@ public sealed class ParticleSystem : IParticleSystem
                     || float.IsNaN(maxDistance)
                     || distance <= maxDistance);
             RefreshRenderableIndex(emitter, wasRenderable);
+
+            // ACDREAM_PROBE_WALK_ROOT companion (Phase I cathedral
+            // instrumentation, throwaway): admission verdicts for the F418
+            // watch set — the real falls owners 0xCF418000-13 and every
+            // F418-cell emitter — every ~120th ApplyRetailView pass.
+            if (_probeAdmissionDumpThisCall
+                && AcDream.Core.Rendering.RenderingDiagnostics.ProbeWalkRootEnabled
+                && ((emitter.AttachedObjectId >= 0xCF418000u
+                        && emitter.AttachedObjectId <= 0xCF418014u)
+                    || (emitter.OwnerCellId >> 16) == 0xF418u))
+            {
+                Console.WriteLine(
+                    $"[falls-adm] owner={emitter.AttachedObjectId:x} "
+                    + $"cell={emitter.OwnerCellId:x8} "
+                    + $"pos=({emitter.OwnerPosition.X:F1},{emitter.OwnerPosition.Y:F1},{emitter.OwnerPosition.Z:F1}) "
+                    + $"dist={distance:F1} max={maxDistance:F1} "
+                    + $"inSet={(visibleCellIds.Contains(emitter.OwnerCellId) ? 1 : 0)} "
+                    + $"eligible={(emitter.ViewEligible ? 1 : 0)} "
+                    + $"active={emitter.ActiveCount} pass={emitter.RenderPass}");
+            }
         }
     }
 
+    // Phase I instrumentation rate limiter (see the probe block above).
+    private static uint _probeAdmissionCallCounter;
+    private static bool _probeAdmissionDumpThisCall;
+
     /// <summary>
     /// Changes only render presentation. Logical lifetime is unaffected.
     /// </summary>