feat(ui): add /settings command and UI panel (#4738)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/cli/src/ui/hooks/useSettingsCommand.ts

@@ -0,0 +1,25 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { useState, useCallback } from 'react';
+
+export function useSettingsCommand() {
+  const [isSettingsDialogOpen, setIsSettingsDialogOpen] = useState(false);
+
+  const openSettingsDialog = useCallback(() => {
+    setIsSettingsDialogOpen(true);
+  }, []);
+
+  const closeSettingsDialog = useCallback(() => {
+    setIsSettingsDialogOpen(false);
+  }, []);
+
+  return {
+    isSettingsDialogOpen,
+    openSettingsDialog,
+    closeSettingsDialog,
+  };
+}