The lock-retry path only fired after the commit step failed, but a
stale .git/index.lock blocks the unstage step (the first index-touching
operation in both git_commit and git_patch). The retry was unreachable.
Extract _clear_stale_lock_from_error helper and extend _unstage_all to
honor force_lock so 'cortex git commit --force' actually clears stale
locks as advertised. Default behavior (force_lock=False) is unchanged
— locks are preserved so callers who don't opt in can still investigate.
Nicholas Ferguson