Report Seat Probe Result

The container reports whether one of its Claude Code seats actually works, right after proving it (or failing to).

Frederick, 2026-09-15, after pasting the wrong value into the claude_code_seat box twice: "Don't make me do this again." Production the same day: the vault accepted the bad paste, the container needed a manual restart to read it, and the only way anyone learned it was wrong was an agent reading container logs -- claude-code| Failed to authenticate. API Error: 401 Invalid bearer token. This route is the other half of closing that: the System page's Claude Code card (ClaudeCodeSeatPanel.tsx) reads last_probe_error/last_probe_detail off GET /api/system/credentials -- the SAME columns/route every other credential's probe verdict already surfaces through (system.service. record_credential_probe_result) -- so this never invents a second way to show a verdict.

Recorded against WHICHEVER credential the probe actually ran against (body.credential) -- claude_code_seat (Seat A, unchanged: the card is about whether Rooster's dedicated issues engineer works, not about which of ITS two credentials happened to carry it this pass -- see SeatProbeResult.auth) or builder_seat (Seat B, RA-45, new). An absent or unrecognised value falls back to claude_code_seat rather than raising -- a malformed report must never 500, and every call site that predates this field meant Seat A anyway.