Code-review findings on T4:
1. Added lock(_lock) around _db.TryGet and TryGetFileBytes in
DatDatabaseWrapper, matching WB's DefaultDatDatabase pattern.
ObjectMeshManager.PrepareMeshDataAsync runs on the thread pool, so
concurrent dat access through the adapter must be serialized — our
underlying DatCollection is not documented as thread-safe.
2. Removed unused `using WorldBuilder.Shared.Models;` from WbMeshAdapter.cs
(its only purpose was TerrainEntry, which moved to AcDream.Core in T2).
Build green; tests green (1147 passing, 8 pre-existing failures baseline).
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>
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