Function install_skill 

pub(super) fn install_skill(
    extension: &str,
    version: &str,
    url: &str,
    expected_sha256: Option<&str>,
    encoded_signature: Option<&str>,
    public_key: &PublicKey,
    dry_run: bool,
    quiet: bool,
)

Downloads, verifies, and installs an extension’s agent skill file into every detected coding assistant’s skills directory.