Function open_pane_floating 

async fn open_pane_floating(
    state: &AppState,
    wstore: &Store,
    event_bus: &EventBus,
    view: String,
    source_tab_id: String,
    meta: HashMap<String, Value>,
) -> Result<PaneOpenResult, String>

Floating-pane branch of open_pane. The block already exists in source_tab_id’s blockids (created by the caller, with no layout node). This moves it into a fresh floating workspace via the tear_off_block saga, sets up the new tab’s layout, broadcasts the new WaveObjs, and asks the source window’s frontend to materialize the chromeless floating OS window via the host open_floating_pane_window command (srv cannot open windows itself). See docs/specs/SPEC_OPENEDITOR_FLOATING_AND_COLLAPSED_TREE_2026_06_16.md.