feat: add Alt+↑/↓ keyboard shortcuts to navigate between sessions

src/App.tsx

@@ -40,7 +40,7 @@ export default function App() {
     return () => setBaseTitle(undefined);
   }, [activeSession, sessions]);
 
-  // Close sidebar on Escape key, open shortcuts on ?
+  // Keyboard shortcuts: Escape, ?, Alt+↑/↓ for session navigation
   const handleKeyDown = useCallback((e: KeyboardEvent) => {
     if (e.key === 'Escape' && sidebarOpen) {
       setSidebarOpen(false);
@@ -52,7 +52,18 @@ export default function App() {
       e.preventDefault();
       setShortcutsOpen(true);
     }
-  }, [sidebarOpen, shortcutsOpen]);
+    // Alt+↑ / Alt+↓ — switch to previous/next session
+    if (e.altKey && (e.key === 'ArrowUp' || e.key === 'ArrowDown')) {
+      e.preventDefault();
+      if (sessions.length < 2) return;
+      const idx = sessions.findIndex(s => s.key === activeSession);
+      if (idx === -1) return;
+      const next = e.key === 'ArrowUp'
+        ? (idx - 1 + sessions.length) % sessions.length
+        : (idx + 1) % sessions.length;
+      switchSession(sessions[next].key);
+    }
+  }, [sidebarOpen, shortcutsOpen, sessions, activeSession, switchSession]);
 
   useEffect(() => {
     document.addEventListener('keydown', handleKeyDown);

src/components/KeyboardShortcuts.tsx

@@ -98,6 +98,10 @@ export function KeyboardShortcuts({ open, onClose }: Props) {
               keys={<><Kbd>{mod}</Kbd><span className="text-zinc-600">+</span><Kbd>K</Kbd></>}
               label={t('shortcuts.search')}
             />
+            <ShortcutRow
+              keys={<><Kbd>Alt</Kbd><span className="text-zinc-600">+</span><Kbd>↑</Kbd><span className="text-zinc-600">/</span><Kbd>↓</Kbd></>}
+              label={t('shortcuts.switchSession')}
+            />
             <ShortcutRow
               keys={<Kbd>Esc</Kbd>}
               label={t('shortcuts.closeSidebar')}

src/lib/i18n.ts

@@ -81,6 +81,7 @@ const en = {
   'shortcuts.send': 'Send message',
   'shortcuts.newline': 'New line',
   'shortcuts.search': 'Search sessions',
+  'shortcuts.switchSession': 'Previous / next session',
   'shortcuts.closeSidebar': 'Close sidebar / search',
   'shortcuts.stop': 'Stop generation',
   'shortcuts.help': 'Show shortcuts',
@@ -163,6 +164,7 @@ const fr: Record<keyof typeof en, string> = {
   'shortcuts.send': 'Envoyer le message',
   'shortcuts.newline': 'Nouvelle ligne',
   'shortcuts.search': 'Rechercher des sessions',
+  'shortcuts.switchSession': 'Session précédente / suivante',
   'shortcuts.closeSidebar': 'Fermer la barre / recherche',
   'shortcuts.stop': 'Arrêter la génération',
   'shortcuts.help': 'Afficher les raccourcis',