Replace the menu bar NSPopover with a proper resizable NSWindow for the
chat interface. Left-click the menu bar icon to toggle the window.
- Chat opens as a standard macOS window (titled, closable, resizable,
miniaturizable) instead of a borderless popover anchored to the menu bar
- Window stays open when clicking desktop, enabling drag-and-drop workflows
- Add WebChatManager.toggleWindow() and closeWindow() for menu bar toggle
- Fix Talk Mode crash on launch (#36983): defer TalkModeController.setEnabled()
to next run loop to prevent Swift exclusivity violation in AppState.init()
