feat(O-T7): drop WB project references; complete extraction

End of Phase O extraction. Final cleanup:

- Dropped <ProjectReference> entries to WorldBuilder.Shared and
  Chorizite.OpenGLSDLBackend from both AcDream.App.csproj and
  AcDream.Core.csproj.
- Added Chorizite.Core NuGet PackageReference to AcDream.Core.csproj
  (needed by Core.Rendering.Wb.TextureHelpers for TextureFormat enum;
  previously transitive through the WB project ref).
- Added BCnEncoder.Net.ImageSharp (1.1.2) + SixLabors.ImageSharp (3.1.12)
  as direct PackageReferences to AcDream.App.csproj — previously transitive
  via Chorizite.OpenGLSDLBackend project; used directly by ObjectMeshManager.

Item A (BaseObjectRenderManager static fields):
- Inlined CurrentAtlas/CurrentVAO/CurrentIBO into a new RenderStateCache.cs
  static class (AcDream.App.Rendering.Wb namespace) — the 4 consumers
  (ManagedGLIndexBuffer, ManagedGLTexture, ManagedGLTextureArray, ParticleBatcher)
  all reference RenderStateCache.* instead of BaseObjectRenderManager.*.
- Dropped using Chorizite.OpenGLSDLBackend.Lib from all 4 consumers and from
  WbDrawDispatcher (which had it only as a dead import).

Item B (ActiveParticleEmitter.ObjectLandblock):
- ObjectLandblock? erased to object?; WorldBuilder.Shared.Models.ObjectId? erased
  to ulong? — both fields are stored but never read by any consumer in our codebase.
- Dropped both WB using directives from ActiveParticleEmitter.cs.

Item C (IDatReaderWriter / IDatDatabase):
- Verbatim copy of both interfaces into IDatReaderWriter.cs in
  AcDream.App.Rendering.Wb namespace — DatCollectionAdapter and ObjectMeshManager
  already live in that namespace, so no using changes needed.
- Dropped using WorldBuilder.Shared.Services from DatCollectionAdapter.cs and
  ObjectMeshManager.cs.

Additional extractions required by the reference drop:
- GeometryUtils.cs: verbatim copy of WorldBuilder.Shared.Lib.GeometryUtils
  (float-precision overloads only; Vector3d double-precision overloads omitted —
  ObjectMeshManager uses only the float versions).
- Dropped using WorldBuilder.Shared.Lib from ObjectMeshManager.cs.

WbMeshAdapter.cs cleanup (spec O-D12):
- Deleted _wbDats (DefaultDatReaderWriter) field + ctor init + Dispose call.
- Deleted the [indoor-upload] NULL_RESULT diagnostic block (lines ~205-262) —
  its Phase 2 cell-resolution investigation is complete; its _wbDats.ResolveId
  dependency goes with this commit.
- Deleted _pendingEnvCellRequests field + isPendingEnvCell tracking in Tick().
- Simplified Tick() to a clean drain loop.

Deleted SplitFormulaDivergenceTest.cs — one-time N.5b data-collection sweep;
job done.

Verified acceptance criteria:
- Zero <ProjectReference> to WorldBuilder.* / Chorizite.OpenGLSDLBackend.* in any csproj.
- Zero 'using WorldBuilder.*' / 'using Chorizite.OpenGLSDLBackend.*' in src/.
- DefaultDatReaderWriter referenced in zero places in src/ (comments only).

Build green (0 warnings, 0 errors).
Tests: 1154 total (-1 from deleted SplitFormulaDivergenceTest), 1146 pass,
8 pre-existing failures (unchanged from baseline — physics/input tests
unrelated to this change).

Spec: docs/superpowers/specs/2026-05-21-phase-o-dat-path-unification-design.md

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

src/AcDream.App/AcDream.App.csproj

@@ -18,6 +18,11 @@
          implement IUniformBuffer from Chorizite.Core; NuGet PackageReferences are not
          forwarded from ProjectReferences so we must declare it explicitly here. -->
     <PackageReference Include="Chorizite.Core" Version="0.0.18" />
+    <!-- Phase O-T7: BCnEncoder.Net.ImageSharp + SixLabors.ImageSharp were previously
+         transitive via the WorldBuilder project reference. Now direct deps of
+         ObjectMeshManager.cs (extracted in T2). -->
+    <PackageReference Include="BCnEncoder.Net.ImageSharp" Version="1.1.2" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="3.1.12" />
     <PackageReference Include="Silk.NET.OpenGL" Version="2.23.0" />
     <PackageReference Include="Silk.NET.OpenGL.Extensions.ARB" Version="2.23.0" />
     <PackageReference Include="Silk.NET.Windowing" Version="2.23.0" />
@@ -35,12 +40,6 @@
     <ProjectReference Include="..\AcDream.Core.Net\AcDream.Core.Net.csproj" />
     <ProjectReference Include="..\AcDream.UI.Abstractions\AcDream.UI.Abstractions.csproj" />
     <ProjectReference Include="..\AcDream.UI.ImGui\AcDream.UI.ImGui.csproj" />
-    <!-- Phase N.4 Task 9: WbMeshAdapter constructs the WB GL pipeline directly.
-         AcDream.Core already references these projects, but project references are
-         not transitive in .NET — AcDream.App must list them explicitly to compile
-         against Chorizite.OpenGLSDLBackend and WorldBuilder.Shared types. -->
-    <ProjectReference Include="..\..\references\WorldBuilder\WorldBuilder.Shared\WorldBuilder.Shared.csproj" />
-    <ProjectReference Include="..\..\references\WorldBuilder\Chorizite.OpenGLSDLBackend\Chorizite.OpenGLSDLBackend.csproj" />
   </ItemGroup>
   <ItemGroup>
     <None Update="Rendering\Shaders\*.*">