feat(cli): TUI complete overhaul — components, sidebar, search, branding (#157)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/cli/src/tui/hooks/use-app-mode.ts

@@ -0,0 +1,37 @@
+import { useState, useCallback } from 'react';
+
+export type AppMode = 'chat' | 'sidebar' | 'search';
+
+export interface UseAppModeReturn {
+  mode: AppMode;
+  setMode: (mode: AppMode) => void;
+  toggleSidebar: () => void;
+  sidebarOpen: boolean;
+}
+
+export function useAppMode(): UseAppModeReturn {
+  const [mode, setModeState] = useState<AppMode>('chat');
+  const [sidebarOpen, setSidebarOpen] = useState(false);
+
+  const setMode = useCallback((next: AppMode) => {
+    setModeState(next);
+    if (next === 'sidebar') {
+      setSidebarOpen(true);
+    }
+  }, []);
+
+  const toggleSidebar = useCallback(() => {
+    setSidebarOpen((prev) => {
+      if (prev) {
+        // Closing sidebar — return to chat
+        setModeState('chat');
+        return false;
+      }
+      // Opening sidebar — set mode to sidebar
+      setModeState('sidebar');
+      return true;
+    });
+  }, []);
+
+  return { mode, setMode, toggleSidebar, sidebarOpen };
+}