sheathe command-line media packager (library entry point).
A pure-Rust alternative to Shaka Packager's packager binary. [run] parses
args and dispatches: probe lists an MP4's streams; package demuxes,
fragments, and writes CMAF init + media segments plus DASH and HLS manifests.
Both the sheathe-cli and sheathe binaries are thin wrappers over [run].