… dirs

A run killed without a parent-death backstop can strand a TOCTOU path-flipper
(a busy `python -c` rename loop that pins a CPU) and an orphaned test rsyncd
(--no-detach --address=127.0.0.1) that squats its fixed port -- the wedge the
claim_ports() bind-probe now reports and points at --cleanup. Sweep both, best
effort, before removing the run dirs.

Each sweep counts the pattern, kills it (with a `sudo -n` retry for a process a
root-running test left), then re-counts after a settle: KILLED reports what
actually died, and a process that survives (pkill blocked, no passwordless sudo,
missing/limited pkill) is reported as SURVIVED and fails the run instead of
falsely claiming success.

Run-dir removal falls back to `sudo -n rm` so a dir whose contents a root test
owns is removed instead of failing with "Permission denied" (the failure mode
seen on the ubuntu/mac targets); only a dir that survives even sudo is failed.

The kill patterns use the pgrep self-exclusion trick ('r[e]name', 'det[a]ch')
so they match a real process's "rename"/"detach" but not the literal pattern in
the cleanup shell's own argv -- run_on() passes the whole script as the remote
argv, so without it --cleanup would signal itself. The patterns are host-global
(not scoped to one run), so --cleanup is documented to run between runs, not
during one.