fix(update): the legacy start_watchdog matches the monitor exactly too; a restart is reported only when the monitor runs (Issue #72, review round 4)

With MAM_DELEGATION_PY=0 the legacy helper still found the monitor with an
unanchored pgrep -f, so a process that only named the monitor path was
reported as the restarted monitor and none was started. lib.sh _monitor_pids
is the shell twin of daemon.find_running; update.sh and post_update.sh check
the PID start_watchdog printed with mam_monitor_started before saying
"monitor: restarted".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/multi-agent-mux-update/scripts/post_update.sh

@@ -37,7 +37,8 @@ fi
 if [ "$MON" = "1" ]; then
   if [ "${MAM_NO_SUBSCRIBER_DAEMON:-0}" = "1" ]; then
     echo "monitor: not restarted (MAM_NO_SUBSCRIBER_DAEMON=1)"
-  elif pid="$(start_watchdog update "$WS")"; then
+  # shellcheck disable=SC2086
+  elif pid="$(start_watchdog update "$WS")" && mam_monitor_started "$WS" $pid; then
     echo "monitor: restarted (PID $pid)"
   else
     echo "ERROR: could not restart the monitor daemon" >&2