The browser omnibar's updateNSView and controlTextDidEndEditing
were both dispatching makeFirstResponder calls without any guard
against re-dispatch. Each makeFirstResponder triggers SwiftUI's
FirstResponderObserver, which re-evaluates the view graph, which
calls updateNSView again, creating an infinite loop via the main
dispatch queue.
Fix: Add a pendingFocusRequest flag on the coordinator to prevent
re-dispatching while a focus/blur request is already in flight.
Also add nsView.currentEditor() != nil to the isFirstResponder
check so the field is recognized as focused during the transition
when the field editor (not the field itself) is first responder.
