OptionalExecuteOptional custom GraphQL executor (used by unit tests; defaults to the provider's ExecuteGQL).
OptionalOnInvoked when an agent's browser_* tool runs, so the UI can show the browser drawer.
OptionalOnInvoked once when the server refuses this conversation a browser (not enabled, not the caller's, over the cap). The controller has already closed it, which stops the live view's polling.
OptionalOnInvoked when the browser opens or closes, or its URL changes.
Options for constructing a ConversationRemoteBrowserController.