Review round 2: the unconditional `command.upgrade(cfg, "head")` in finally ran
a redundant no-op on the success path and, on a genuinely broken re-upgrade,
replaced the try's original exception with its own. Gate the restore on a
`reupgraded` flag so it fires only when the upgrade didn't complete — the
cascade-prevention intent is kept without the double-run or error-masking.