fix(render): detail overlay is fogged after the combine like retail; VM1 review fixes

Opus dual-lens review of 05970306 + 388457a7 (APPROVE WITH FIXES). Four
items, all landed:

1. FOG (behavioural). Retail's D3D fixed-function fog stage runs AFTER the
   texture-stage pipeline, so the detail contribution must be fogged, not
   just the base. mesh_modern.frag already fogs the base colour
   (applyFog(rgb, vWorldPos)) before mesh_detail's replay draws over it;
   mesh_detail.frag previously emitted raw detail.rgb, understating fog by
   f*a*(fog-detail). Fix: mesh_detail.vert now outputs vWorldPos (mirroring
   mesh_modern.vert); mesh_detail.frag declares the identical SceneLighting
   UBO and applyFog function (copied verbatim, same binding/std140/math) and
   fogs detail.rgb before emitting it. This collapses algebraically to
   retail's fog-after-combine order:
     (1-a)*mix(base,fog,f) + a*mix(detail,fog,f) = mix(lerp(base,detail,a),fog,f)
   RetailDetailTextureContract gains ExpectedFogged(base,detail,opacity,fog,
   fogFactor); RetailDetailTextureContractTests pins the identity across 200
   random samples within 1e-6.

2. EnvCellRenderer.Rhi.cs's DrawEnvCell-category comment still said "apply
   the 10-50 m positive-view-depth fade" — a stale claim from before VM1
   removed the fade. Replaced with the mip-chain attenuation statement that
   mesh_detail.vert's header comment already carries.

3. Added the test the VM1 contract required but never had: TerrainAtlas
   .TryCreateDetailTexture uploads a full mip chain (MipLevelCount ==
   RhiWorldTextureArray.MipLevelsFor(w,h), GenerateMipChain called) and
   registers with the repeat/linear world sampler, not single-level or
   clamped. Drives the private method directly (reflection) against a
   synthetic PFID_A8R8G8B8 RenderSurface through a minimal in-memory
   IDatReaderWriter fake, so the lane stays hermetic (no installed DAT).

4. #226 pseudocode note: noted that retail's stage-1 OUTPUT alpha
   (MODULATE(TEXTURE, CURRENT), 0x0059c549) — the framebuffer blend weight a
   delayed-alpha subset composites with — is not modelled; acdream instead
   draws a second pass weighted by detail.a*diffuseAlpha. Identical for
   opaque subsets, a bounded difference on translucent building/EnvCell
   subsets already covered by the existing AP-34 shared-alpha-queue
   divergence row. Also qualified the tmpmaterial.Diffuse.a = 1f (0x0059cb99)
   citation to name its exact branch (burnedInStaticLights < 0 &&
   *(render_device+0x7e4) == 0); the other branch leaves diffuse FromVertex,
   but the opaque->1 / fading->opacity mapping still holds either way.

Nit also folded in: EnvCellRendererTests' new SubmitRhi instance-alpha test
is now a [Theory] over WbRenderPass.Opaque and .Transparent, pinning the
bind-before-first-draw invariant on both passes.

Regenerated mesh_detail's committed SPIR-V and the shader manifest
(tools/compile-shaders.ps1); no other shader pair changed.

Verified: dotnet build AcDream.slnx -c Release (0 warnings, 0 errors);
dotnet test on AcDream.App.Tests (Release, hermetic lanes) green, including
the shader manifest tests explicitly; AcDream.Core.Tests unaffected/green.

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

tests/AcDream.App.Tests/Rendering/Wb/EnvCellRendererTests.cs

@@ -116,8 +116,11 @@ public class EnvCellRendererTests
     /// pass, mesh_modern's shell pipeline and (when enabled) mesh_detail's
     /// replay alike.
     /// </summary>
-    [Fact]
-    public void SubmitRhi_BindsConstantOneInstanceAlphaBeforeAnyDrawInThePass()
+    [Theory]
+    [InlineData(WbRenderPass.Opaque)]
+    [InlineData(WbRenderPass.Transparent)]
+    public void SubmitRhi_BindsConstantOneInstanceAlphaBeforeAnyDrawInThePass(
+        WbRenderPass renderPass)
     {
         const int instanceCount = 5;
 
@@ -144,7 +147,13 @@ public class EnvCellRendererTests
         // Seed one real draw command, exactly what
         // RenderModernMDIInternal would have built from a live landblock,
         // so the test can assert an actual ordering against a real draw
-        // rather than a vacuous "no draw happened" pass.
+        // rather than a vacuous "no draw happened" pass. Same command for
+        // both passes: with _buildingDetailEnabled left at its default
+        // (false), the Transparent branch's own detail-interleave logic
+        // (SubmitRhi's "detailEnabled" block) never fires, so it draws
+        // through the identical MultiDrawIndexedIndirect call the Opaque
+        // pass does — only the pipeline rebound inside the per-range loop
+        // differs, which is not what this test is pinning.
         Type rendererType = typeof(EnvCellRenderer);
         FieldInfo commandsField = rendererType.GetField(
             "_commands", BindingFlags.NonPublic | BindingFlags.Instance)!;
@@ -184,7 +193,7 @@ public class EnvCellRendererTests
             "SubmitRhi", BindingFlags.NonPublic | BindingFlags.Instance)!;
         submitRhi.Invoke(
             renderer,
-            new object[] { allInstances, WbRenderPass.Opaque, 1, instanceCount });
+            new object[] { allInstances, renderPass, 1, instanceCount });
 
         IReadOnlyList<GpuRecordedCall> calls = device.Calls;
         int alphaBindIndex = -1;