chore(O-T7): code-review housekeeping after WB extraction

Five small post-cleanup items from T7 code review:

I1: Removed dead `datDir` parameter from WbMeshAdapter ctor (parameter
    was unused after _wbDats removal; ArgumentNullException.ThrowIfNull
    was misleading). Updated call sites in GameWindow.cs and
    WbMeshAdapterTests.cs.

I2: Updated stale GameWindow.cs comment that still described
    WbMeshAdapter as opening its own dat handles. Now reflects Phase O
    state: shared DatCollection via DatCollectionAdapter.

I3: Documented thread-safety contract on RenderStateCache (render-thread
    only — required for the mutable-static GL sentinel pattern).

M1: Added comment on IDatReaderWriter's write-path methods noting they
    are preserved for verbatim compatibility but unused in acdream.

M3: Added comment on Chorizite.Core PackageReference in Core.csproj
    explaining the previously-transitive dependency.

Also excluded SplitFormulaDivergenceTest.cs from the test build via
<Compile Remove>: this N.5b one-time data-collection test referenced
WorldBuilder.Shared types directly; after Phase O-T7 dropped that
project reference it no longer compiles. The sweep data it produced
already informed the N.5b Path-C decision and the file is retained
in the tree for historical reference.

Build green; tests green (1146 + 8 pre-existing failures baseline
maintained).

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/Rendering/Wb/RenderStateCache.cs

@@ -12,6 +12,12 @@ namespace AcDream.App.Rendering.Wb;
 ///   <c>CurrentIBO</c>    — OpenGL name of the currently bound index buffer object.
 /// Sentinel value 0 means "no valid binding cached."
 /// </summary>
+/// <remarks>
+/// All accesses must occur on the render thread. GL state binding is
+/// not thread-safe; these sentinels are written immediately after the
+/// corresponding glBind* call and read by the next dispatch on the
+/// same thread.
+/// </remarks>
 public static class RenderStateCache
 {
     public static uint CurrentAtlas = 0;