Canonical pickup for a fresh session. R1 (per-cell DrawInside render) shipped + is
correct (cellar seals); it exposed a pre-existing cell-membership ping-pong (the
flap). Root cause: CellTransit.BuildCellSetAndPickContaining picks from an UNORDERED
HashSet, dropping retail find_cell_list's current-cell-first ordering (CELLARRAY
index-0 + interior-wins-break, pc:308742-308825). Next job: verbatim port of that
ordered pick, replacing the HashSet + the 5ca2f44 pre-check approximation. User
authorized breaking any physics to get membership faithful. Full diagnosis, verbatim
retail source, fix plan, KEEP/don't-redo, test baseline, and a copy-paste pickup
prompt in the doc.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
