phase(N.1): add LandBlock → TerrainEntry[] adapter

Phase N.1 step 1: WbSceneryAdapter.BuildTerrainEntries converts our
LandBlock dat type into the TerrainEntry[81] shape WorldBuilder's
TerrainUtils / SceneryRenderManager consume.

Field mapping (TerrainInfo → TerrainEntry):
  TerrainInfo.Road    (bits 0-1)   → TerrainEntry.Road
  TerrainInfo.Type    (bits 2-6)   → TerrainEntry.Type
  TerrainInfo.Scenery (bits 11-15) → TerrainEntry.Scenery
  LandBlock.Height[i]              → TerrainEntry.Height

The spec listed the texture property as 'Texture' but TerrainEntry's
actual property is named 'Type' (confirmed from source). The spec also
described LandBlock.Terrain as ushort[81] but it is TerrainInfo[81] —
DatReaderWriter already decodes the bit fields so the adapter uses
TerrainInfo's named properties rather than raw bit-shift expressions.

Spec: docs/superpowers/specs/2026-05-08-phase-n1-scenery-via-wb-helpers-design.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Tests/World/WbSceneryAdapterTests.cs

@@ -0,0 +1,74 @@
+using AcDream.Core.World;
+using DatReaderWriter.DBObjs;
+using DatReaderWriter.Types;
+
+namespace AcDream.Core.Tests.World;
+
+/// <summary>
+/// Tests for <see cref="WbSceneryAdapter"/>. The adapter converts our
+/// LandBlock dat type (Terrain TerrainInfo[81] + Height byte[81]) into
+/// WorldBuilder's <see cref="WorldBuilder.Shared.Models.TerrainEntry"/>[81]
+/// shape, which WB's TerrainUtils / SceneryRenderManager consume.
+///
+/// Bit layout in LandBlock.Terrain[i] (TerrainInfo / ushort):
+///   bits 0-1   : Road        (2 bits) → WB TerrainEntry.Road
+///   bits 2-6   : TerrainType (5 bits) → WB TerrainEntry.Type
+///   bits 11-15 : SceneType   (5 bits) → WB TerrainEntry.Scenery
+/// Height comes from LandBlock.Height[i] (byte) → WB TerrainEntry.Height.
+/// </summary>
+public class WbSceneryAdapterTests
+{
+    [Fact]
+    public void BuildTerrainEntries_PreservesRoadTextureSceneryHeight()
+    {
+        var block = new LandBlock();
+
+        // Vertex 0: road=0x3, type=0x00, scenery=0x1F, height=42
+        // raw layout: bits 0-1=11, bits 2-6=00000, bits 7-10=0000, bits 11-15=11111
+        // = 0xF803
+        block.Terrain[0] = (TerrainInfo)0xF803;
+        block.Height[0]  = 42;
+
+        // Vertex 80: road=0x0, type=0x1F, scenery=0x00, height=200
+        // raw layout: bits 0-1=00, bits 2-6=11111, bits 11-15=00000
+        // = 0x007C
+        block.Terrain[80] = (TerrainInfo)0x007C;
+        block.Height[80]  = 200;
+
+        var entries = WbSceneryAdapter.BuildTerrainEntries(block);
+
+        Assert.Equal(81, entries.Length);
+
+        Assert.Equal((byte)42,   entries[0].Height);
+        Assert.Equal((byte)0x3,  entries[0].Road);
+        Assert.Equal((byte)0x00, entries[0].Type);
+        Assert.Equal((byte)0x1F, entries[0].Scenery);
+
+        Assert.Equal((byte)200,  entries[80].Height);
+        Assert.Equal((byte)0x0,  entries[80].Road);
+        Assert.Equal((byte)0x1F, entries[80].Type);
+        Assert.Equal((byte)0x00, entries[80].Scenery);
+    }
+
+    [Fact]
+    public void BuildTerrainEntries_AllZeros_ProducesEmptyEntries()
+    {
+        var block = new LandBlock();
+        // Terrain and Height are already zero-initialized by LandBlock constructor.
+        var entries = WbSceneryAdapter.BuildTerrainEntries(block);
+        Assert.All(entries, e =>
+        {
+            Assert.Equal((byte)0, e.Height);
+            Assert.Equal((byte)0, e.Road);
+            Assert.Equal((byte)0, e.Type);
+            Assert.Equal((byte)0, e.Scenery);
+        });
+    }
+
+    [Fact]
+    public void BuildTerrainEntries_NullBlock_Throws()
+    {
+        Assert.Throws<ArgumentNullException>(() =>
+            WbSceneryAdapter.BuildTerrainEntries(null!));
+    }
+}