Match shortcuts by typed character across keyboard layouts and teach the expand chord

Trust event.key for Latin letters and digits so Dvorak's ⌘V stays paste;
fall back to the physical key only for other characters. Shift now only
distinguishes letter chords, so AZERTY's shifted '.' works as labelled.
Show the chord on the collapsed sidebar button, hide the account menu's
'?' hint on touch, and name the Chat shortcut's enabled state.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>