fix(render): #105 white indoor walls — restore WB's per-frame staged-texture flush dropped in the N.4/O-T4 extraction

Root cause: TextureAtlasManager.AddTexture only STAGES texture content (PBO
write + ManagedGLTextureArray._pendingUpdates); the actual TexSubImage3D
copies + mipmap regeneration happen in ProcessDirtyUpdates, which WB drives
once per frame via ObjectMeshManager.GenerateMipmaps() from its render loop
(WB GameScene.cs:975, just before the opaque pass). GameScene is the file we
replaced with GameWindow, so the call site was silently dropped — staged
updates only reached the GPU as a side effect of PBO growth (UpdateLayerInternal
flushes pending updates before orphaning the PBO). Every layer staged after an
array's LAST growth kept undefined TexStorage3D content behind a valid,
resident bindless sampler handle: white/garbage walls, zh==0, dat tripwires
silent — exactly the #105 signature. Only ObjectRenderBatch.BindlessTextureHandle
consumers are affected (EnvCellRenderer cell shells = indoor walls); entities
resolve via TextureCache (immediate TexImage2D) and terrain via TerrainAtlas
(immediate GenerateMipmap), which is why only indoor walls ever struck.

Fix: WbMeshAdapter.Tick() now calls _meshManager.GenerateMipmaps() after the
staged-upload drain — Tick runs before all draw passes (GameWindow OnRender),
the exact WB-equivalent position.

Evidence (ACDREAM_PROBE_TEXFLUSH=1 apparatus, kept env-gated):
- pre-fix (texflush-prefix.log): pending updates climb 0->48->...->142 and
  park at 126 across 34/34 atlas arrays at standstill, forever (19 heartbeats);
  brief dips only at PBO-growth crossings — the broken contract live.
- post-fix (texflush-postfix.log): every line after=0 — staged updates drain
  the same frame, all 34 arrays clean.

Intermittency explained: background decode-completion order shuffles which
textures land in the never-flushed tail; whether a visible wall samples one is
per-run luck. Also explains the #110 correlation: znear=0.1 makes close-up
geometry newly visible -> more prepare/upload pressure indoors -> bigger tail
-> higher strike probability. The near plane is mechanism-innocent (re-land
follows as its own commit).

Baseline maintained: App 223 / UI 420 / Net 294 / Core 1377 green + 4
pre-existing #99-era failures + 1 skip; CornerFloodReplayTests (5) and
CameraCornerSealReplayTests (2) gates green.

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

src/AcDream.Core/Rendering/RenderingDiagnostics.cs

@@ -172,6 +172,21 @@ public static class RenderingDiagnostics
     public static bool ProbeClipRouteEnabled { get; set; } =
         Environment.GetEnvironmentVariable("ACDREAM_PROBE_CLIPROUTE") == "1";
 
+    /// <summary>
+    /// #105 white-indoor-textures apparatus (2026-06-10). When true, <c>WbMeshAdapter.Tick</c>
+    /// emits one <c>[tex-flush]</c> line whenever the staged-texture-update picture changes:
+    /// pending layer updates across all shared atlases BEFORE and AFTER the per-frame
+    /// <c>ObjectMeshManager.GenerateMipmaps()</c> flush, plus arrays-with-pending / total-array
+    /// counts. The broken contract this pins: <c>TextureAtlasManager.AddTexture</c> only STAGES
+    /// pixel data (PBO + pending list); without the per-frame flush (WB GameScene.cs:975) the
+    /// data never reaches the GL texture and the batch samples undefined content behind a valid
+    /// bindless handle — the classic white walls. A healthy run shows <c>after=0</c> on every
+    /// line; a stuck <c>before==after&gt;0</c> at standstill is the #105 mechanism live.
+    /// Initial state from <c>ACDREAM_PROBE_TEXFLUSH=1</c>.
+    /// </summary>
+    public static bool ProbeTexFlushEnabled { get; set; } =
+        Environment.GetEnvironmentVariable("ACDREAM_PROBE_TEXFLUSH") == "1";
+
     /// <summary>
     /// Bounded-propagation port apparatus (2026-06-08). When true, PortalVisibilityBuilder.Build emits
     /// one [portal-churn] summary line per call: per-cell pop count (re-pops = churn), total re-enqueues,