Boards, step 6a: the forge writes the Usage and Crew starting boards on boot, and never overwrites an edited one #2458

Part 1 of #1566. The ring and the machine source landed in 910954a0. Every panel here uses a source already in src/boards/sources.ts.

Done looks like:

• [ ] On boot, if a starting board is missing from the boards repo (src/boards/store.ts), the forge writes it: Usage (machine CPU and memory for the pod, cells and node, from machine and usage) and Crew (runs by agent and outcome, review verdicts and spend per hour, from runs, reviews and spend).
• [ ] A starting board a person has edited or deleted is never written again. Record that it was offered so a deletion sticks.
• [ ] A test boots a fresh forge and runs every panel of both boards' queries without error. A second boot after an edit leaves the edit in place.