perf(diag): per-frame history export + checkpoint LOH/cache counters + soak capped mode (2026-07-24 audit review)

An adversarial performance review found our own instruments cannot
measure the project's own performance gates:

- FrameProfiler aggregated CPU/GPU/alloc/stage samples into ~5-second
  windows and reset the ring buffers after each report, so route-wide
  p50/p95/p99 distributions across a whole soak could not be
  reconstructed after the fact. ACDREAM_FRAME_HISTORY=<path> now opts
  into a separate per-frame history (one record per frame, ~72
  bytes/record, accumulated in memory with zero frame-thread I/O) that
  a shutdown-only Dispose() writes as CSV. The aggregated [frame-prof]
  report format and its existing metrics are unchanged.

- The canonical checkpoint JSON tracked cache residency (entry/byte
  counts) but never LOH size/fragmentation, process-wide allocated
  bytes, or cache hit/miss/eviction traffic — a committed audit JSON
  showed 65% LOH fragmentation that no tracked instrument recorded,
  and "does a revisit portal hit or miss the caches" was unanswerable
  from an artifact alone. WorldLifecycleResourceSnapshot now carries
  loh_size_bytes/loh_fragmentation_bytes (GCMemoryInfo.GenerationInfo
  index 3), process_total_allocated_bytes (GC.GetTotalAllocatedBytes),
  and Interlocked hit/miss/eviction counters for the CPU mesh cache,
  decoded-texture cache, and the four bounded DAT-object caches
  (portal/cell/highRes/language, aggregated).

- run-connected-r6-soak.ps1 unconditionally forced
  ACDREAM_UNCAPPED_RENDER=1 with no capped mode, while its sibling
  lifecycle-gate script correctly gated it behind a switch. Added
  -Uncapped (default capped, matching the sibling script's pattern),
  fixed the stationary dwell (12s -> 26s, past the 25s
  LiveEntityLivenessController deadline the adjacent comment already
  cited), and now write an env-disclosure.json into the automation
  artifact directory before every launch listing every ACDREAM_* var
  the script sets plus -Uncapped, since the prior audit could only see
  ACDREAM_DUMP_MOVE_TRUTH and nothing else was ever recorded anywhere.

Cache counters are wired via the existing composition path
(ObjectMeshManager already owns the CPU mesh cache and the mesh
extractor directly; content.Dats is threaded into
WorldLifecycleResourceSnapshotSource the same way every other
composition consumer receives it). The DAT-object cache lives behind
IDatReaderWriter, a third-party interface from the DatReaderWriter
package that cannot be extended; RuntimeDatCollection (the one
production implementation) exposes the aggregate stats directly and a
pattern match reads them, degrading to zero for any test double —
no new static registry was introduced (GpuMemoryTracker remains the
one precedented process-wide static).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
(cherry picked from commit 1da2c33c875b41fa383dd79694ee2765f0e21896)

src/AcDream.Content/DecodedTextureCache.cs

@@ -21,6 +21,19 @@ internal sealed class DecodedTextureCache {
     private readonly int _maximumEntries;
     private long _residentBytes;
 
+    // Hit/miss/eviction traffic counters (2026-07-24 measurement-tooling
+    // review). Read via Stats without the _gate lock, so plain fields with
+    // Interlocked increments rather than lock-protected longs.
+    private long _hits;
+    private long _misses;
+    private long _evictions;
+
+    /// <summary>Cumulative hit/miss/eviction counts since construction.</summary>
+    public CacheStats Stats => new(
+        Interlocked.Read(ref _hits),
+        Interlocked.Read(ref _misses),
+        Interlocked.Read(ref _evictions));
+
     public DecodedTextureCache(long maximumBytes, int maximumEntries) {
         ArgumentOutOfRangeException.ThrowIfNegative(maximumBytes);
         ArgumentOutOfRangeException.ThrowIfNegative(maximumEntries);
@@ -47,10 +60,12 @@ internal sealed class DecodedTextureCache {
     public bool TryGet(DecodedTextureKey key, out byte[] pixels) {
         lock (_gate) {
             if (!_entries.TryGetValue(key, out var node)) {
+                Interlocked.Increment(ref _misses);
                 pixels = null!;
                 return false;
             }
 
+            Interlocked.Increment(ref _hits);
             Touch(node);
             pixels = node.Value.Pixels;
             return true;
@@ -131,6 +146,7 @@ internal sealed class DecodedTextureCache {
         _lru.Remove(node);
         _entries.Remove(node.Value.Key);
         _residentBytes -= node.Value.Pixels.LongLength;
+        Interlocked.Increment(ref _evictions);
     }
 }