feat(rendering): port retail one-pass detail material

Replace the building and EnvCell detail replay with retail's exact single-pass stage result, including authored surface opacity, squared detail alpha, final-alpha clipping, and the original subset pipeline/order. Arm the ordered walk command in place to close #471, delete the replay pipelines/shaders, and advance prepared content to recipe 9.

Mutation witnesses (each restored before commit):
- X=a*qA: RetailDetailTextureContractTests.BothShaderFamiliesUseTheSharedOnePassSourceAndDebugPrecedesDetailSample line 174, missing materialAlpha * detail.a * detail.a.
- X*=base alpha: same test line 175, forbidden baseTexel.a found.
- CLIP against base alpha: EnvCellAlphaDrawSourceTests.ClipShaders_UseGreaterEqualForThePerRangeReference line 260, final-X conditional missing.
- second detail draw: EnvCellAlphaDrawSourceTests.DetailOn_EveryEnvCellFamilyDrawsOnceInPlaceWithAuthoredOpacity line 105, Assert.Single saw 2 MDI calls.
- straight-alpha substitution: WalkStaticStreamPopulatorTests.ImmediateBuildingDetail_RetainsOriginalFramebufferFamily line 1244, Additive first failed (only wb-mesh-alpha-1x recorded; InvAlpha also failed).
- omit ordered arm: OrderPreservingSubmitterTests.PrepareThenDraw_OrdinaryBuildingClipBuildingOrdinary_ArmsOnePassInPlace line 305, expected (77,3.5), got (0,0).
- omit atmospheric combine: RetailDetailTextureContractTests.BothShaderFamiliesUseTheSharedOnePassSourceAndDebugPrecedesDetailSample line 173, atmospheric shared include missing.
- drop serialized opacity: ObjectMeshDataSerializerTests.SurfaceOpacity_RoundTripsBitExactlyAndDeterministically line 288, first reported 0.5 bits 1056964608 vs 1065353216.
- stale detail arm: ordered adjacency test line 307, expected following ordinary (0,0), got (77,3.5).
- per-frame surface map: EnvCellAlphaDrawSourceTests.ProductionWholeLeaf_WarmedScanSubmitRhiAndFilteredReplayDoNotAllocate line 178, expected 0 B, got 147456 B.

Verification before commit: shader compiler 23/23; focused App 213/213; Content 75/75; Core Wb 10/10; launcher migration 6/6; Release solution build 0 warnings / 0 errors; git diff --check clean.

tests/AcDream.Content.Tests/MeshExtractorSolidFaceExtractionTests.cs

@@ -207,7 +207,7 @@ public sealed class MeshExtractorSolidFaceExtractionTests
         var dats = new FakeMeshExtractorDats();
         RegisterTexturedQuad(
             dats,
-            SurfaceType.Base1Image,
+            SurfaceType.Base1Image | SurfaceType.Translucent,
             PixelFormat.PFID_DXT1,
             new byte[8],
             translucency: 0.25f);
@@ -219,7 +219,40 @@ public sealed class MeshExtractorSolidFaceExtractionTests
         KeyValuePair<(int Width, int Height, TextureFormat Format), List<TextureBatchData>> group =
             Assert.Single(mesh.TextureBatches);
         Assert.Equal(TextureFormat.RGBA8, group.Key.Format);
-        Assert.Equal(4 * 4 * 4, Assert.Single(group.Value).TextureData.Length);
+        TextureBatchData batch = Assert.Single(group.Value);
+        Assert.Equal(4 * 4 * 4, batch.TextureData.Length);
+        Assert.Equal(0.75f, batch.SurfaceOpacity);
+    }
+
+    [Theory]
+    [InlineData(0f, 1f)]
+    [InlineData(0.25f, 0.75f)]
+    [InlineData(0.5f, 0.5f)]
+    [InlineData(0.75f, 0.25f)]
+    [InlineData(1f, 0f)]
+    public void PrepareCellStructMeshData_CarriesAuthoredSurfaceOpacity(
+        float translucency,
+        float expectedOpacity)
+    {
+        var dats = new FakeMeshExtractorDats();
+        RegisterCellTexturedSurface(
+            dats,
+            SurfaceType.Base1Image | SurfaceType.Translucent,
+            translucency);
+        var extractor = new MeshExtractor(dats, NullLogger.Instance, sideStagedSink: null);
+
+        ObjectMeshData mesh = Assert.IsType<ObjectMeshData>(
+            extractor.PrepareCellStructMeshData(
+                id: 1,
+                BuildQuadCellStruct(RetailCullMode.Landblock),
+                surfaceOverrides: [2],
+                Matrix4x4.Identity,
+                CancellationToken.None));
+
+        TextureBatchData batch = Assert.Single(Assert.Single(mesh.TextureBatches).Value);
+        Assert.Equal(
+            BitConverter.SingleToInt32Bits(expectedOpacity),
+            BitConverter.SingleToInt32Bits(batch.SurfaceOpacity));
     }
 
     /// <summary>
@@ -232,12 +265,16 @@ public sealed class MeshExtractorSolidFaceExtractionTests
     /// not change what these tests actually pin (verified by hand against
     /// CellStructSideCandidates.TriangleFanIndices before this change).
     /// </summary>
-    private static void RegisterCellTexturedSurface(FakeMeshExtractorDats dats)
+    private static void RegisterCellTexturedSurface(
+        FakeMeshExtractorDats dats,
+        SurfaceType type = SurfaceType.Base1Image,
+        float translucency = 0f)
     {
         dats.Register(TexturedSurfaceId, new Surface
         {
-            Type = SurfaceType.Base1Image,
+            Type = type,
             OrigTextureId = SurfaceTextureId,
+            Translucency = translucency,
         });
         dats.Register(SurfaceTextureId, new SurfaceTexture
         {