fix(cli): extensions dialog UX polish (#19685)

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

@@ -0,0 +1,41 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  useTextBuffer,
+  type TextBuffer,
+} from '../components/shared/text-buffer.js';
+import { useUIState } from '../contexts/UIStateContext.js';
+
+const MIN_VIEWPORT_WIDTH = 20;
+const VIEWPORT_WIDTH_OFFSET = 8;
+
+export interface UseSearchBufferProps {
+  initialText?: string;
+  onChange: (text: string) => void;
+}
+
+export function useSearchBuffer({
+  initialText = '',
+  onChange,
+}: UseSearchBufferProps): TextBuffer {
+  const { mainAreaWidth } = useUIState();
+  const viewportWidth = Math.max(
+    MIN_VIEWPORT_WIDTH,
+    mainAreaWidth - VIEWPORT_WIDTH_OFFSET,
+  );
+
+  return useTextBuffer({
+    initialText,
+    initialCursorOffset: initialText.length,
+    viewport: {
+      width: viewportWidth,
+      height: 1,
+    },
+    singleLine: true,
+    onChange,
+  });
+}