`tutabridge-git` VCS package builds only the headless CLI (no GUI/Node).
Handles the SDK submodule in prepare(), fetches crates for an offline
`--frozen` build, installs the binary + a systemd *user* unit (the
bridge runs per-user, binds localhost, uses the login keyring).
packaging/aur/README documents local build + AUR publish (.SRCINFO is
generated on Arch).
