True while the app is still completing its initial routing and wiring. Selections are refused before side effects or load dispatch in this state.
True while a guarded dataset switch is already in flight. Consulted before the selection side effects (host-URL replacement, onSrcChange): the dispatch below will reject, and the host URL or src snapshot must not end up pointing at a dataset that never loaded.
Open the dataset browser modal. Returns the new instance so the caller can track it on its own field; the helper never mutates orchestrator state directly. All side effects on the orchestrator (options.src update, datasetBrowser reset, host-URL replacement) flow through the supplied ports.
Caller is responsible for checking that no browser is already open before calling this function — re-opening would stack modals.