test(render): foliage-wind receiver fallback guard asserts branch shape; cascade-0 publish covered (Campaign VM VM6 review 5 nits)

Round-5 narrow re-review of 754d59d9: APPROVE (verified to the SPIR-V
disassembly; shadows-on path proven opcode-identical). Four
non-blocking nits.

N1 (test robustness): T3 (ReceiverVertexShadersFallBackToThePlainLightDirectionWhenTheShadowFlagIsClear)
was satisfied by comment prose -- round 5's own explanatory comments
quote the exact plain-pipeline direction substring
("-uLights[i].dirAndRange.xyz, ... matched bit-for-bit"), so the
substring-only assertion passed even with the code mutated. Fixed:
comment lines are now stripped (new StripLineComments helper) before
any assertion, and a new ordered regex per shader asserts the exact
branch SHAPE -- shadowGatedOff ? -uLights[...] : normalize(uShadow...)
-- not just substring presence. Mutation-tested locally against the
rewritten test: (1) swapping the ternary's true/false operands --
FAILED (previously passed); (2) deleting the fallback entirely,
collapsing to the pre-round-5 buggy expression -- FAILED (previously
passed). Original file restored and reverified passing after each
mutation.

N2 (doc accuracy): "numerically the plain pipeline" overstated the
round-5 fix in three places (plan doc, mesh_atmospheric.vert,
terrain_atmospheric.vert). The direction expression is bit-for-bit;
the SUM is not, because the atmospheric shaders' split ambient+point
vs directional accumulation (and terrain's two varyings vs the plain
pipeline's one) reassociates float summation order by ~1 ulp -- which
is exactly the measured mean |Delta| 0.007 the coordinator's own
pixel-proof evidence already recorded (well under the 65 px noise
floor). All three rewritten to say the receiver "matches the plain
pipeline to within float summation-order rounding (measured mean
|Delta| 0.007 on the offline scene)."

N3 (coverage): RenderPrepared's own cascadeCount == 0 exit (the F2
fix) had no direct test even though RenderPrepared already has 8
direct call sites in this file. Added one: ResidentMaximumReachMeters
at/below CameraNearMeters, passed straight to RenderPrepared with an
otherwise-fully-valid environment (so the fitter, not the environment
gate, is what returns zero cascades), asserting IsBindableFor true /
IsValidFor false.

N4 (latent): RenderPrepared's OWN "if (!environment.ShouldRender)"
exit is a fourth bufferless-disabled path -- unreachable via Render
(whose own gate already validates ShouldRender first) but the same
shape, and RenderPrepared is called directly by tests and any future
caller. Took the preferred fix: publishes the disabled binding there
too, via the same helper, so every exit on a frame that draws the
world publishes when the pack's AtmosphericFrame is bound. Also made
EvaluateGateAndPublishDisabledBinding self-contained: it now resets
_currentFrameBinding to Disabled on its own entry instead of relying
on Render having done so first (idempotent with Render's own reset).

Regenerated SPIR-V: mesh_atmospheric.vert and terrain_atmospheric.vert
are comment-only changes (N2), so only the manifest's source hashes
changed -- compiled .spv bytes are unchanged, consistent with round 3's
precedent for comment-only shader edits.

Verify: Release build 0 warnings/0 errors. App hermetic-lane filter
6,055/0 failed. Full hermetic-filtered solution: 15,283/0 failed
across 15 projects.

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

src/AcDream.App/Rendering/DirectionalSunShadowRenderer.cs

@@ -329,7 +329,12 @@ internal sealed class DirectionalSunShadowRenderer : IDirectionalShadowReceiverS
     /// <paramref name="environmentGateTicks"/> are the validated values
     /// Render's remaining stages use). Behaviour-preserving: identical
     /// order, identical PublishDisabledReceiverBinding calls, identical
-    /// Disabled(...) construction as before the extraction.
+    /// Disabled(...) construction as before the extraction. Round 6 (N4):
+    /// self-contained — resets <see cref="_currentFrameBinding"/> itself
+    /// on entry instead of relying on the caller to have done it first,
+    /// so a future direct caller of this method (not just Render) cannot
+    /// observe a stale binding from a previous frame. Idempotent with
+    /// Render's own reset immediately before calling this.
     /// </summary>
     internal DirectionalSunShadowDiagnostics? EvaluateGateAndPublishDisabledBinding(
         IGpuFrame frame,
@@ -337,6 +342,7 @@ internal sealed class DirectionalSunShadowRenderer : IDirectionalShadowReceiverS
         out DirectionalShadowEnvironmentState environment,
         out long environmentGateTicks)
     {
+        _currentFrameBinding = DirectionalShadowFrameBinding.Disabled;
         long cpuStageStarted = input.MeasureCpuStages ? Stopwatch.GetTimestamp() : 0L;
         environment = DirectionalShadowEnvironmentGate.Evaluate(
             input.Environment,
@@ -636,7 +642,18 @@ internal sealed class DirectionalSunShadowRenderer : IDirectionalShadowReceiverS
         ArgumentNullException.ThrowIfNull(worldDraws);
         ArgumentNullException.ThrowIfNull(terrainDraws);
         if (!environment.ShouldRender)
+        {
+            // Campaign VM VM6 review fix round 6 (N4): a fourth bufferless-
+            // disabled exit, same shape as Render's own two and the
+            // cascadeCount == 0 exit below (F2). Unreachable via Render
+            // itself (its own gate already validated ShouldRender before
+            // calling here), but RenderPrepared is also called directly
+            // (tests, and any future caller) — one rule covers every exit
+            // on a frame that draws the world: publish when the pack's
+            // AtmosphericFrame is bound.
+            PublishDisabledReceiverBinding(frame, atmosphericFrame);
             return Disabled(in environment, cpuStages);
+        }
         if (!worldDraws.Commands.IsEmpty && worldGeometry is null)
             throw new ArgumentNullException(nameof(worldGeometry));
         if (!terrainDraws.Commands.IsEmpty && terrainGeometry is null)