diag #176/#180: isolation toggles pin the residual stripes on the camera sweep, not the render

The #176 gate-2 failure ("stripes/triangles flickering when the camera
is pushed into walls; nothing when zoomed out") is NOT a render defect.
Isolation apparatus added this commit:

- ACDREAM_LIGHT_DEBUG shader modes (mesh_modern.vert/frag + uLightDebug
  upload in EnvCellRenderer/WbDrawDispatcher): 1 = ambient-only,
  2 = dynamics killed, 3 = raw vLit field (texture ignored). The
  pattern SURVIVES mode 3 -> not texture; lives above the light data.
- ACDREAM_CLIP_DEBUG=1 (RenderingDiagnostics.ClipDebugNoShellTrim +
  the EnvCellRenderer slot-fill gate): shell pass draws cells WHOLE
  (retail's shape). Pattern survives -> the per-cell clip trim is
  exonerated.

With every render suspect dead, an autonomous visual loop (synthetic
back-into-wall input + GDI window captures + the [flap-sweep] probe)
pinned the mechanism numerically: at a compressed moving boom the
camera-collision sweep is BISTABLE - consecutive sweeps with ~1.4 mm
input drift flip the first-contact solution 0.27 m along the boom
(pulledIn 0.27<->0.53, every ~5-10 frames, all 368k sweeps ok=True),
and at ~1700 fps unsynced every monitor refresh tear-interleaves the
two views = the stripe/hatch patterns. Filed as #180 with the retail
anchor: viewer_sought_position is STATEFUL (SmartBox 0x00452d75 feeds
the CURRENT swept viewer into CameraManager::UpdateCamera 0x00456660
and assigns the return to the sought, 0x00452d84) - the target
converges to the collided position instead of re-rolling the full
knife-edge ray per frame like our RetailChaseCamera does. SweepEye
itself ports update_viewer 0x00453ce0 faithfully and is exonerated.

Also recorded in #176: the site-A weenie light-registration leak (a
portal's I100 light stacked x2->x4 over one session as re-CreateObject
re-registered it under fresh entity ids).

The #176 lighting fix (d8984e87) remains live-verified; #176 re-gates
after #180 lands. ISSUES: #180 filed, #176 updated. Suites: Core
2599+2skip; toggles inert by default.

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

src/AcDream.App/Rendering/Wb/EnvCellRenderer.cs

@@ -878,6 +878,8 @@ public sealed unsafe class EnvCellRenderer : IDisposable
             _shader.SetInt("uRenderPass", (int)renderPass);
             _shader.SetInt("uFilterByCell", 0);
             _shader.SetInt("uLightingMode", 1);   // A7 Fix D D-3/D-4: EnvCell bake (wrap points, no sun)
+            // #176 stripe-hunt isolation (ACDREAM_LIGHT_DEBUG) — throwaway diagnostic.
+            _shader.SetInt("uLightDebug", AcDream.Core.Rendering.RenderingDiagnostics.LightDebugMode);
 
             // Phase U.4 ROOT-CAUSE FIX (cell-shell flicker / "transparent walls when
             // moving"): upload uViewProjection HERE rather than inheriting it from
@@ -1306,7 +1308,10 @@ public sealed unsafe class EnvCellRenderer : IDisposable
         // instanceClipSlot[i] tracks Instances[i] through the MDI BaseInstance.
         if (_clipSlotData.Length < uniqueInstanceCount)
             _clipSlotData = new uint[Math.Max(_clipSlotData.Length * 2, uniqueInstanceCount)];
-        if (_cellIdToSlot is null)
+        // #176 stripe-hunt isolation (ACDREAM_CLIP_DEBUG=1): force every shell
+        // instance to slot 0 (no-clip) — retail draws cell shells WHOLE.
+        if (_cellIdToSlot is null
+            || AcDream.Core.Rendering.RenderingDiagnostics.ClipDebugNoShellTrim)
         {
             Array.Clear(_clipSlotData, 0, uniqueInstanceCount);
         }

src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs

@@ -910,6 +910,8 @@ public sealed unsafe class WbDrawDispatcher : IDisposable
         // A7 Fix D D-3/D-4: object path — plain Lambert points + sun. MUST set
         // explicitly (shared GL uniform; EnvCellRenderer sets it to 1).
         _shader.SetInt("uLightingMode", 0);
+        // #176 stripe-hunt isolation (ACDREAM_LIGHT_DEBUG) — throwaway diagnostic.
+        _shader.SetInt("uLightDebug", AcDream.Core.Rendering.RenderingDiagnostics.LightDebugMode);
 
         // #128 self-heal: fresh re-request dedup per Draw pass.
         _missRequested.Clear();