fix(rendering): restore retail terrain texture tiling

Carry TerrainTex.TexTiling through the terrain atlas and upload a layer-indexed table to the modern bindless shader so base, overlay, and road textures repeat at retail scale. Keep alpha masks cell-scaled and preserve retail's verified source-level-zero high-detail selection.

Add the named-retail pseudocode, WorldBuilder/ACE/ACME cross-reference, adapter conformance tests, and inventory documentation so a future renderer migration keeps the contract.

Co-Authored-By: Codex <noreply@openai.com>

tests/AcDream.App.Tests/Rendering/TerrainTextureTilingTableTests.cs

@@ -0,0 +1,66 @@
+using AcDream.App.Rendering;
+
+namespace AcDream.App.Tests.Rendering;
+
+public sealed class TerrainTextureTilingTableTests
+{
+    [Fact]
+    public void Build_MapsDatRepeatCountsToAtlasLayers()
+    {
+        var table = TerrainTextureTilingTable.Build(
+        [
+            (Layer: 0u, RepeatCount: 4u),
+            (Layer: 7u, RepeatCount: 2u),
+            (Layer: 32u, RepeatCount: 8u),
+        ]);
+
+        Assert.Equal(TerrainTextureTilingTable.LayerCapacity, table.Length);
+        Assert.Equal(4f, table[0]);
+        Assert.Equal(2f, table[7]);
+        Assert.Equal(8f, table[32]);
+    }
+
+    [Fact]
+    public void Build_DefaultsOnlyUnusedLayersToOne()
+    {
+        var table = TerrainTextureTilingTable.Build(
+        [
+            (Layer: 3u, RepeatCount: 0u),
+        ]);
+
+        Assert.Equal(1f, table[2]);
+        Assert.Equal(0f, table[3]);
+        Assert.Equal(1f, table[4]);
+    }
+
+    [Fact]
+    public void Build_RejectsLayersTheShaderCannotAddress()
+    {
+        var ex = Assert.Throws<InvalidOperationException>(() =>
+            TerrainTextureTilingTable.Build(
+            [
+                (Layer: (uint)TerrainTextureTilingTable.LayerCapacity, RepeatCount: 1u),
+            ]));
+
+        Assert.Contains("exceeds the shader capacity", ex.Message);
+    }
+
+    [Fact]
+    public void ModernShader_AppliesTheOwningLayersRepeatCountToEveryTerrainSample()
+    {
+        string shaderPath = Path.Combine(
+            AppContext.BaseDirectory,
+            "Rendering",
+            "Shaders",
+            "terrain_modern.frag");
+        string shader = File.ReadAllText(shaderPath);
+
+        Assert.Contains("uniform float uTexTiling[36];", shader);
+        Assert.Contains("baseUV * terrainTiling(pOverlay0.z)", shader);
+        Assert.Contains("baseUV * terrainTiling(pOverlay1.z)", shader);
+        Assert.Contains("baseUV * terrainTiling(pOverlay2.z)", shader);
+        Assert.Contains("baseUV * terrainTiling(pRoad0.z)", shader);
+        Assert.Contains("vBaseUV * terrainTiling(vBaseTexIdx)", shader);
+        Assert.DoesNotContain("const float TILE", shader);
+    }
+}