Function lumen_current_page 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn lumen_current_page(
    buf: *mut c_char,
    buf_len: usize,
    out_len: *mut usize,
) -> LumenStatus

Read the current active page key into buf (UTF-8 + trailing NUL), following the shared string-out convention: on success *out_len (when non-null) is the byte length excluding the NUL; when buf is null or too small, *out_len is set to the required capacity and LumenStatus::ErrBufferTooSmall is returned. Empty before the first page mounts. Thread-safe (reads the lumen_core::nav current-page mirror, which lags a resolved navigation by at most one tick).