feat(render): Phase A8 Wave 2 — EnvCellRenderer (WB EnvCellRenderManager port)

The core port. 1013 LOC of WB-faithful rendering algorithm:

- GetEnvCellGeomId        : WB EnvCellRenderManager.cs:94-103 verbatim
- PrepareRenderBatches    : WB EnvCellRenderManager.cs:247-373 verbatim
                            (parallel frustum-cull, per-cell slow path,
                            ThreadLocal merge, atomic snapshot swap)
- Render(filter:)         : WB EnvCellRenderManager.cs:395-511 verbatim
                            (filter-driven gfxObj group + draw call build)
- RenderModernMDIInternal : WB BaseObjectRenderManager.cs:709-848
                            (single-slot variant; resize buffers,
                            group by cull mode + additive, MDI draw)
- PopulatePartGroups      : WB EnvCellRenderManager.cs:572-580 verbatim
                            (Setup part recursion via PopulateRecursive)
- RegisterCell / FinalizeLandblock / RemoveLandblock — streaming seam
  (no WB analog; bridges acdream's existing StreamingController +
  LandblockStreamer to the renderer's per-cell instance store)

Documented deviations from WB:
- Drop _useModernRendering branch (Phase N.5 mandatory modern path)
- Drop SelectedInstance/HoveredInstance highlights (no editor state)
- _activeSnapshotGlobalGroups/GfxObjIds as sibling fields on the class
  rather than on the snapshot (EnvCellVisibilitySnapshot per Task 4 spec
  only carries BatchedByCell + VisibleLandblocks; global groups only
  used in the unfiltered Render(pass) path which we don't take)
- ConcurrentDictionary<uint, EnvCellLandblock> keyed by full 32-bit
  landblock id (WB uses ushort packed key; acdream uses full id throughout)

10 unit tests (GetEnvCellGeomId determinism + bit-33 dedup flag +
NeedsPrepare + dispose semantics + RemoveLandblock idempotence). Build
green; 23/23 Wave 1+2 tests pass.

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

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

@@ -0,0 +1,116 @@
+// Tests for EnvCellRenderer (Phase A8, 2026-05-28).
+// These cover the pure data-handling portions of EnvCellRenderer.
+// The GL-dependent Render() and RenderModernMDIInternal() paths require a
+// GL context and are visual-verified at the render frame (Task 10).
+
+using System.Collections.Generic;
+using AcDream.App.Rendering.Wb;
+using Xunit;
+
+namespace AcDream.App.Tests.Rendering.Wb;
+
+public class EnvCellRendererTests
+{
+    // -----------------------------------------------------------------------
+    // GetEnvCellGeomId — verbatim port of WB EnvCellRenderManager.cs:94-103
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void GetEnvCellGeomId_DedupBitSet()
+    {
+        var id = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, new List<ushort> { 1, 2, 3 });
+        // Bit 33 (0x2_0000_0000) must be set — distinguishes dedup geom from per-cell ids.
+        Assert.NotEqual(0UL, id & 0x2_0000_0000UL);
+    }
+
+    [Fact]
+    public void GetEnvCellGeomId_Deterministic()
+    {
+        var s = new List<ushort> { 1, 2, 3 };
+        var a = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, s);
+        var b = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, s);
+        Assert.Equal(a, b);
+    }
+
+    [Fact]
+    public void GetEnvCellGeomId_DiffersByEnvironmentId()
+    {
+        var a = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, new List<ushort> { 1 });
+        var b = EnvCellRenderer.GetEnvCellGeomId(0x43, 7, new List<ushort> { 1 });
+        Assert.NotEqual(a, b);
+    }
+
+    [Fact]
+    public void GetEnvCellGeomId_DiffersByCellStructure()
+    {
+        var a = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, new List<ushort> { 1 });
+        var b = EnvCellRenderer.GetEnvCellGeomId(0x42, 8, new List<ushort> { 1 });
+        Assert.NotEqual(a, b);
+    }
+
+    [Fact]
+    public void GetEnvCellGeomId_DiffersBySurfaces()
+    {
+        var a = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, new List<ushort> { 1 });
+        var b = EnvCellRenderer.GetEnvCellGeomId(0x42, 7, new List<ushort> { 2 });
+        Assert.NotEqual(a, b);
+    }
+
+    // -----------------------------------------------------------------------
+    // Constructor — pure data, no GL
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void NewRenderer_NeedsPrepareIsTrue()
+    {
+        // GL and meshManager are null — only valid for pure-data tests (no
+        // Initialize() is called, so no GL calls are made).
+        var r = new EnvCellRenderer(gl: null!, meshManager: null!, frustum: new WbFrustum());
+        Assert.True(r.NeedsPrepare);
+    }
+
+    [Fact]
+    public void NewRenderer_NotDisposed()
+    {
+        var r = new EnvCellRenderer(gl: null!, meshManager: null!, frustum: new WbFrustum());
+        Assert.False(r.IsDisposed);
+    }
+
+    // -----------------------------------------------------------------------
+    // RemoveLandblock — pure data path
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void RemoveLandblock_NonExistent_DoesNotThrow()
+    {
+        var r = new EnvCellRenderer(gl: null!, meshManager: null!, frustum: new WbFrustum());
+        // Should silently no-op.
+        r.RemoveLandblock(0xA9B40000u);
+        Assert.True(r.NeedsPrepare);
+    }
+
+    // -----------------------------------------------------------------------
+    // GetEnvCellGeomId — additional edge cases
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void GetEnvCellGeomId_EmptySurfaces_Deterministic()
+    {
+        var a = EnvCellRenderer.GetEnvCellGeomId(1, 0, new List<ushort>());
+        var b = EnvCellRenderer.GetEnvCellGeomId(1, 0, new List<ushort>());
+        Assert.Equal(a, b);
+        Assert.NotEqual(0UL, a & 0x2_0000_0000UL);
+    }
+
+    [Fact]
+    public void GetEnvCellGeomId_SurfaceOrderMatters()
+    {
+        var a = EnvCellRenderer.GetEnvCellGeomId(1, 1, new List<ushort> { 10, 20 });
+        var b = EnvCellRenderer.GetEnvCellGeomId(1, 1, new List<ushort> { 20, 10 });
+        // The hash is order-sensitive (matches WB's foreach loop), so
+        // swapped order should produce a different id.
+        Assert.NotEqual(a, b);
+    }
+
+    // (Render() requires a GL context — visual-verified in Task 10.)
+}