Archiving from the session sheet navigates away first, which unmounted SessionOptions and released its Sessions
reference; Chord cancels a released reference's calls, so the archive call rejected with "p2.sessions: released",
shown as the composer toast over the owner-notice lane. The archive now holds a reference of its own until it is done,
and the server runs its steps in a root of its own.
The archive stopped the worker with Hosts.stop, which restarts it for its holders: the page's lingering
conversation started a worker the archived session refused (resolve_failed, "Worker: Session is archived" notice).
SessionWorkerControl.suspend stops it and leaves its holders suspended until a restore (retry) or their release;
archive, a failed fork's archived copy and an archived session's index rebuild use it.
0a730c8a76