- Atomic writes for mfer gen: writes to temp file, renames on success,
cleans up temp on error/interrupt. Prevents empty manifests on Ctrl-C.
- Humanized byte sizes using dustin/go-humanize (e.g., "10 MiB" not "10485760")
- Progress lines clear when done (using ANSI escape \r\033[K])
- Debug logging when files are added to manifest (mfer gen -vv)
- Move -v/-q flags from global to per-command for better UX
- Add tests for atomic write behavior with failing filesystem mock