Function lumen_node_set_inner_markup 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn lumen_node_set_inner_markup(
    node: LumenNode,
    markup: *const c_char,
) -> LumenStatus

Replace node’s children with the subtree parsed from markup (element.innerHTML = ...). Parsed by the injected front-end and spawned through the same path the <for> reconciler uses; a no-op on the precompiled-artifact path (no parser linked). Guarded: do not feed untrusted content; this injects live markup. Thread-safe.