v1.4.2 — Relay: watchers die with the work

Companion fix to v1.4.1's "register and verify": nothing told the watchers to stop, so a resolved job would leave both machines firing headless watcher passes every 5 minutes — forever.

A watcher's lifecycle is now bound to open jobs, symmetric with registration:

• Any watcher pass (controller or worker, session or headless) that finds no open relay issue binding its node tears itself down: removes its own scheduler entry (schtasks /Delete /TN "relay-<repo>" /F / launchctl bootout + plist removal), records none (torn down <date>) in the node table, commits, and stops /loop polling.
• The controller closing the last open job performs its own teardown and leaves a closing comment so other nodes tear down on their next pass.
• Re-joining later is cheap: the next "autonomous-loop relay" on a new job re-registers from scratch.
• New "immortal cron" failure drill in references/relay-scenarios.md.

No open jobs, no watchers.