B7 (Jun 18 2026): user reported Settings page unresponsive when
reached via the ChatScreen topbar gear icon, but worked fine via
the drawer sidebar. Two fixes:
1. Route topbar gear through NavigationController.navigateTo()
instead of raw backStack.add(). The NavigationController path
(used by the drawer) deduplicates against the current top
entry and matches the drawer's navigation flow exactly. The
bypass path could stack duplicate SettingsScreen entries on
rapid taps, which likely caused the unresponsive symptom.
2. Add 'Clear Token' OutlinedButton below the Auth Token field in
Settings. One-tap wipes a corrupted / rejected token and saves
immediately, without having to select-and-delete the masked
password field character by character. Recovers from the
'I gave you a bad token' scenario in seconds.