feat(streaming): shadow-publish flat collision assets

Carry one immutable prepared collision closure with each accepted near-tier generation and install graph plus flat views through the same retained publication receipt. Apply the same strict package-only rule to live entities, add exact sampled graph-authoritative comparison artifacts and lifecycle counters, and prove cancellation, demotion, rehydrate, revisit, teardown, reconnect, and the nine-stop route with 14,064 zero-mismatch samples.

Co-authored-by: OpenAI Codex <codex@openai.com>

src/AcDream.Core/Physics/PhysicsDiagnostics.cs

@@ -21,6 +21,27 @@ namespace AcDream.Core.Physics;
 /// </summary>
 public static class PhysicsDiagnostics
 {
+    /// <summary>
+    /// Slice I5 graph/flat referee cadence. Zero disables the diagnostic;
+    /// N samples every Nth collision-traversal entry. The graph path remains
+    /// authoritative regardless of the comparison result.
+    /// </summary>
+    public static int CollisionShadowSampleEvery { get; set; } =
+        ParsePositiveInt(
+            Environment.GetEnvironmentVariable(
+                "ACDREAM_COLLISION_SHADOW_EVERY"));
+
+    /// <summary>
+    /// Directory for deterministic Slice I5 mismatch artifacts.
+    /// </summary>
+    public static string CollisionShadowArtifactDirectory { get; set; } =
+        Environment.GetEnvironmentVariable(
+            "ACDREAM_COLLISION_SHADOW_DIR")
+        ?? Path.Combine(
+            Environment.CurrentDirectory,
+            ".test-out",
+            "collision-shadow");
+
     /// <summary>
     /// When true, <see cref="PhysicsEngine.ResolveWithTransition"/> emits
     /// one structured <c>[resolve]</c> line per call: input + target +
@@ -962,4 +983,14 @@ public static class PhysicsDiagnostics
         }
         return "?";
     }
+
+    private static int ParsePositiveInt(string? value) =>
+        int.TryParse(
+            value,
+            System.Globalization.NumberStyles.None,
+            System.Globalization.CultureInfo.InvariantCulture,
+            out int parsed)
+        && parsed > 0
+            ? parsed
+            : 0;
 }