An admin can now opt into "teaching mode" from the lobby, seeding
themselves as the Rank-3 player who must play the Deep in the first
scene (instead of leaving it to the random starting-rank roll), so they
can run the table for new crews.
- Game.teaching_deep_player_id (+ Alembic migration)
- maybe_finish_assign_techniques honors it before rolling ranks, so both
the normal flow and the dev-mode skip path respect it
- Admin-gated POST .../teaching-mode toggle (pre-rank phases only)
- Lobby checkbox UI, greyed out if another admin already volunteered
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Tim McCarthy
bfe982251e