Mark a running worker '⚠ stalled' when its log has not changed for more than
AGENT_QUEUE_STALL_MIN minutes (default 10), using log mtime as the freshness
signal. Implemented in both the bash status table and the Node dashboard.
Honor 'timeout: 45m' (90s|45m|2h|1d) by wrapping the agent in timeout/gtimeout
when available (hard process-tree kill), else a portable bash watchdog. On expiry
the job moves doing->failed with result=timeout and a TIMED OUT log line.
Serialize jobs by lock key (frontmatter 'lock:' override, default cwd) via the
single run-loop's pre-launch eligibility check; the oldest non-busy job is picked
regardless of --max. Adds a flock-based worker guard where flock exists (Linux);
macOS relies on the single-daemon model. Records lock= in job meta.
