feat(pool): the pool - stacks, admission, the runner and the scheduler

The allowlists and the instrument checks (mcp_connected, db_answered,
exercised), the stack keys, Stacks and Admission, the Runner that runs one
claude or opencode process per pass, and the Scheduler with its retries,
rate-window pauses, the prompt-prefix warm-up, the seats and the board.
One thread per pass; each worker runs on its own copy of the job.

Every pass runs under the supervisor, so a timeout or an abort takes its
whole tree down; a timed-out pass reports exit -9, a SIGKILLed child's
code. The helpers the lenses run are this binary's `sql` and `totp`.
:Process gains an Append stream for the OpenCode meta line.

The tests cover the pool and its share of the commits-mode, seat-pool and
several-drivers checks, a fake claude under the supervisor included.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

interfaces/Crafter.Review.cppm

@@ -29,5 +29,6 @@ export import :Mcp;
 export import :Seats;
 export import :SeatPool;
 export import :OpenCode;
+export import :Pool;
 export import :Freeze;
 export import :Driver;