~/.omp/run/daemons/<hash> scopes accumulated forever: broker shutdown
removed only the socket and PID lease, and nothing swept dead scopes, so
inert broker state and the persistent shared Chromium profiles grew
without bound (reporter: 1.3GB / 198 dirs in ~4 weeks).
Each broker now sweeps its sibling daemon roots on startup and removes a
scope only when its broker.pid is absent/dead, no live client presence
remains, and it has been untouched past a stale grace. The caller's own
runtime dir and the machine-global daemon container are skipped. The
sweep is detached and non-throwing so it never delays client connects.
Fixes#8674
can1357