Function activate_in_stored_layout 

async fn activate_in_stored_layout(
    state: &AppState,
    tab_id: &str,
    block_id: &str,
)

LayoutStackActivate through the reducer, then mstore — the same dispatch → apply → publish shape as pane.moveTab. Best-effort: the renderer switches the pane itself on block:reveal, so a reducer that can’t apply it (no tree for the tab yet) only costs the head start.