Function spawn_streaming 

pub fn spawn_streaming<P: AsRef<OsStr>, F>(
    program: P,
    args: &[&str],
    on_line: F,
) -> ToolCallResult
where
    F: FnMut(&str),

Generic-over-program variant of run_apr_streaming. Production callers pass crate::apr_bin::apr_binary; tests use it to inject a mock.