backup_template used a hardcoded _BACKUP_BASE_DIR=/var/lib/ci/backups; now derives <config.paths.root>/backups (matches the CLI --backup-base-dir default) per the plan's no-hardcoded-path gotcha. Tests no longer need to monkeypatch the constant.
Extracts pure, click-free cargo-cache status/purge and host disk/runner/
backup-template logic into operations/, mirroring the W1 pattern. Routes
commands/retention.py::_purge_cargo_cache through operations.cache while
preserving identical CLI output. commands/monitor.py is left untouched
(its refactor is optional per the plan; the Windows/Linux polymorphic
_service_status and the disk not-found detection don't map cleanly onto
the new pure functions without risking behavioural drift).
Simone