When a daemon is killed or crashes without cleaning up, stale .sock/.pid
files are left behind. Previously, `close --all` would fail to connect to
these zombie daemons and simply report an error, leaving the stale files
in place and poisoning all future sessions.
Three fixes:
1. `close --all` now force-kills unreachable daemon processes and removes
all stale files (pid, sock, stream) instead of reporting failure. It
also cleans up dead-but-lingering PID files during enumeration and
scans for orphaned .sock files without corresponding .pid files.
2. `ensure_daemon` handles concurrent startup races: when a spawned
daemon exits with "Address already in use" (another instance won the
bind race), it checks whether the winner is accepting connections and
piggybacks on it instead of failing.
3. `cleanup_stale_files` is now public so `close --all` can reuse it.
Fixes#1118
Co-authored-by: ctate <366502+ctate@users.noreply.github.com>
