test(editor): assert checkbox toggle updates the editor document

Read the ProseMirror document's taskItem `checked` attribute after
tapping the mobile task checkbox, not just the native checkbox widget.
The widget toggles regardless of whether the fix's setNodeMarkup
transaction runs, so the previous assertions could not detect a
widget/document desync. Verified this fails against the pre-fix code
and passes with the fix.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/e2e/formatting.spec.ts

@@ -13,6 +13,29 @@ async function runTiptapCommand(page: Page, commandFn: string) {
 	);
 }
 
+/**
+ * Read the `checked` attribute of the first task item from the live ProseMirror
+ * document. This reflects the editor's document state, not just the native
+ * checkbox widget — so it catches a widget/document desync where the DOM
+ * checkbox toggles but the transaction never updates the node.
+ */
+async function firstTaskItemChecked(page: Page): Promise<boolean> {
+	return page.getByTestId('tiptap-editor').evaluate((el) => {
+		const editor = (el as any).__tiptapEditor;
+		if (!editor) throw new Error('TipTap editor not found on element');
+		let checked: boolean | undefined;
+		editor.state.doc.descendants((node: any) => {
+			if (checked === undefined && node.type.name === 'taskItem') {
+				checked = Boolean(node.attrs.checked);
+				return false;
+			}
+			return true;
+		});
+		if (checked === undefined) throw new Error('No task item found in document');
+		return checked;
+	});
+}
+
 /** Toggle markdown mode via the overflow menu. */
 async function toggleMarkdownMode(page: Page) {
 	await page.getByTestId('overflow-menu-btn').click();
@@ -140,17 +163,20 @@ test.describe('Rich text formatting on mobile', () => {
 			});
 		});
 
-		// When the checkbox is tapped, only its state changes and focus never enters the editor
+		// When the checkbox is tapped, the change propagates to the editor's document
+		// without focus ever entering the editor (which would open the mobile keyboard)
 		await checkbox.tap();
 
 		await expect(checkbox).toBeChecked();
+		expect(await firstTaskItemChecked(page)).toBe(true);
 		await expect(richTextEditor).not.toBeFocused();
 		await expect(richTextEditor).toHaveAttribute('data-focus-count', '0');
 
-		// And unchecking it also leaves the contenteditable editor unfocused
+		// And unchecking propagates to the document too, still without focusing the editor
 		await checkbox.tap();
 
 		await expect(checkbox).not.toBeChecked();
+		expect(await firstTaskItemChecked(page)).toBe(false);
 		await expect(richTextEditor).not.toBeFocused();
 		await expect(richTextEditor).toHaveAttribute('data-focus-count', '0');
 	});