Add remote-job.sh: a detached job whose result outlives the session

`ssh host 'cmd | tail -f log | sed -n /ready/q'` reported success on jobs that
never finished, three structural ways: the broker aborts the long connection, a
readiness pattern can match a log header printed before the work starts, and
`sed -n /x/q` exits the instant it matches — tearing down the very command it
was watching. The replacement runs the job detached on the host and writes
NAME.out, NAME.rc, then NAME.done LAST, so status is a cheap read of files over
a short-lived connection. That survives the connection, the restart, and the job
that restarts the endpoint the agent itself is running on.

Black-box tests pin the sentinel ordering (rc before done), that a finished-but-
failed job is DONE rc=N with the report still exiting 0, and that a name with no
state is never reported DONE.

Refs #53

omp-docs/tools/index.md

@@ -20,6 +20,7 @@ Configuration guides and reference material for installed software. Each tool ha
 * [niri](niri/index.md) — Scrollable-tiling Wayland compositor — configuration, keybindings, and architecture for the workstation.
 * [noctalia-shell](noctalia-shell.md) — Native desktop environment for Niri — launcher, control center, settings, lock screen, session menu, hotkey overlay, media controls, and system management.
 * [packages](packages.md) — `packages/*.pkgs` desired state and the two tools that keep a machine and its manifest agreeing: `install.sh` installs the delta, `pkg-inventory.sh` reports what the machine has outgrown.
+* [remote-job](remote-job.md) — Detached job runner for `ssh` work: completion sentinels on the host replace the `tail -f | sed -n /ready/q` pattern that reported success on jobs that never finished.
 * [tmux](tmux.md) — Terminal multiplexer configuration, extended-keys setup, keyboard input best practices, and reload/restart procedures.
 
 ## Adding a New Tool