fix(ui): restore composer focus after CodeMirror migration

packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx

@@ -504,6 +504,7 @@ export const ComposerEditor = React.forwardRef<ComposerEditorHandle, ComposerEdi
             <div
                 ref={hostRef}
                 data-testid={props['data-testid']}
+                data-chat-input="true"
                 onMouseDown={handleHostMouseDown}
                 className={cn(
                     'composer-editor w-full',

packages/ui/src/components/chat/composer/editor/__tests__/dom.test.ts

@@ -0,0 +1,25 @@
+import { afterEach, expect, test } from 'bun:test';
+
+import { focusChatInput } from '../dom';
+
+const originalDocument = globalThis.document;
+
+afterEach(() => {
+    globalThis.document = originalDocument;
+});
+
+test('focuses the CodeMirror chat input content', () => {
+    let selector = '';
+    let focused = false;
+    globalThis.document = {
+        querySelector: (value: string) => {
+            selector = value;
+            return { focus: () => { focused = true; } };
+        },
+    } as unknown as Document;
+
+    focusChatInput();
+
+    expect(selector).toBe('[data-chat-input="true"] .cm-content');
+    expect(focused).toBe(true);
+});

packages/ui/src/components/chat/composer/editor/dom.ts

@@ -0,0 +1,5 @@
+const CHAT_INPUT_EDITOR_SELECTOR = '[data-chat-input="true"] .cm-content';
+
+export function focusChatInput(): void {
+    document.querySelector<HTMLElement>(CHAT_INPUT_EDITOR_SELECTOR)?.focus();
+}