Widen #75162: _prune_if_needed() drops finished sessions (TTL expiry and
oldest-finished eviction at MAX_PROCESSES) — release their Popen/PTY
handles there too, covering sessions inserted into _finished without
passing through _move_to_finished(). The release helper is idempotent,
so double-close on the normal path is a no-op. Adds two tests: prune
releases handles of dropped sessions, and a still-running session's
pipe stays open.
teknium
b3a8734d43