Verify the sandbox on macOS, then lift the approval gate

The job boundary holds on a macOS runner under Seatbelt, and once it does, a job resumes with another maintainer's answer without the runner owner's approval: the approval step is gone from kix, the inbox, and the runner.

• Rerun the hostile-repository boundary test from moq-dev/quest#212 on macOS. Sandboxed commands must not reach the account's Keychain item (security find-generic-password), /private/var/folders, or another home, and the realpath'd /private/tmp directory must work as TMPDIR.
• Decided 2026-10-24 (user) on #212: the answer-approval gate stays until this verification passes. Then remove approvedAt handling from the runner, the approval decision from the inbox, and the hold from kix, and update the "until the job sandbox ships" comments in cloudflare/README.md, cloudflare/src/jobs/routes.ts, and store.ts.
• Decided 2026-10-27 (user) in /quest-plan: rerun the test for an opencode account too, through its srt command wrapper, and lift the gate only once both agents hold.
• If the boundary does not hold, record what leaks here and keep the gate.