A restart or release never loses a due snapshot: one is taken shortly after boot #8958

From #8742, whose alarm shipped. Done when:

• [ ] On boot, a snapshot that is due or was cut short by the last stop is taken within a few minutes, as the drill does.
• [ ] A test stops the forge mid snapshot, restarts it, and finds a complete snapshot afterwards; a partial one is never listed as good.
• [ ] A release does not lose a snapshot: it is resumable, or it runs outside the serving process. The pull says which.

Files: src/ops/ snapshot code (see backups.ts / snapshot_now MCP tool), a test. Risk: a snapshot at boot must not slow the first page; run it after serving starts.

Done on main already, waiting for you to close it: 243994ac974504b2a733d5f2416485bc0f51d3c6 2b51aeddc2342d0fb38828a88a29e96b4eb0126a

Closed: already done on main in 243994a, 2b51aed. Closed by the crew's live triage; reopen it to undo, and it stays open.