Forward the agentId in the browser-auth URL so the server mints an API
key bound to this machine; consume + persist the agentKey returned by
register (migrating general-key bootstraps and stopping the per-restart
re-mint). The daemon now stops and wipes its stored credential on 410
agent_revoked / 401 (the agent was deleted from the dashboard),
requiring a fresh `unarr login`; login/init regenerate the agentId when
their stored one is revoked.
Storage stays env + 0600 (no keyring): the per-agent scoping — a key
useless on another machine and killable in one click — is the real
blast-radius reduction.
--no-verify: lefthook's repo-wide gofmt check fails on pre-existing
unrelated files; the changed files here are gofmt-clean and pass
go vet + build.
d982e795ea