Function promote_pool_window 

pub fn promote_pool_window(
    state: &Arc<AppState>,
    workspace_id: &str,
    screen_x: i32,
    screen_y: i32,
    width: Option<i32>,
    height: Option<i32>,
    tab_anchor_x: Option<i32>,
    tab_anchor_y: Option<i32>,
) -> Option<String>

Promote a pool window for tear-off. Pops a label, sends a move-and-show task to the CEF UI thread, and emits pool:promote to the renderer with the workspace ID. Returns the promoted window’s label so the caller can chain SC_MOVE against it. Returns None if the pool is empty (caller should fall back to the cold path).

Called from the IPC handler tear_off_pool_promote.