GpuWorldState.RemoveLandblock rescued persistent entities (the player)
only from the _loaded list, silently dropping one sitting in the
_pendingByLandblock bucket. The player is re-injected via AppendLiveEntity
every frame; right after a teleport its destination landblock has not
streamed in yet, so the player lands in the pending bucket — and if that
landblock is then unloaded during the streaming churn, the persistent
entry was dropped, violating the "persistent therefore survives unload"
contract. Leading candidate for the #138 "own avatar vanishes after a
couple round-trips" symptom (cumulative; needs user visual confirm).
Fix: scan the pending bucket for persistent guids and rescue them too,
so DrainRescued re-parks them at the next valid landblock. Provable
correctness fix with a deterministic test (rescue-from-pending plus a
negative for non-persistent). Core tests green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>