Bridges LoadedLandblock load/unload events to IWbMeshAdapter ref counts.
Tier-aware by design: walks WorldEntity collection filtered by
ServerGuid == 0 (procedural / atlas-tier only). Server-spawned entities
are skipped — those will go through EntitySpawnAdapter (Task 17).
Per-landblock id-set snapshot ensures unload pairs 1:1 with load even
when underlying data is released. Duplicate-load idempotency for
defensive resilience to streaming-controller bugs.
Six tests: registers per unique id; dedups across entities; skips
server-spawned; unload matches load; unknown landblock no-ops;
duplicate load no-ops.
Wiring into GpuWorldState lands in Task 12.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
