test(frontend): cover escapeLatin1 round-trip in KowlJsonView

Lock in the regression fix from #2421: with escapeLatin1, Latin-1
glyphs are written as \u00XX in the editor value (recoverable via
copy-paste); without it, the glyph passes through.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: twmb

frontend/src/components/misc/kowl-json-view.test.tsx

@@ -161,4 +161,24 @@ describe('KowlJsonView', () => {
 
     expect(editorLayoutSpy).toHaveBeenLastCalledWith({ width: 800, height: 480 });
   });
+
+  test('escapeLatin1 re-escapes Latin-1 code points so copy-paste recovers the original byte', async () => {
+    render(<KowlJsonView escapeLatin1 srcObj={{ v: 'ÛN' }} />);
+
+    await waitFor(() => {
+      const value = editorPropsSpy.mock.lastCall?.[0].value as string;
+      expect(value).toContain('\\u00db');
+      expect(value).not.toContain('Û');
+    });
+  });
+
+  test('without escapeLatin1, Latin-1 glyphs pass through to the editor unchanged', async () => {
+    render(<KowlJsonView srcObj={{ v: 'ÛN' }} />);
+
+    await waitFor(() => {
+      const value = editorPropsSpy.mock.lastCall?.[0].value as string;
+      expect(value).toContain('Û');
+      expect(value).not.toContain('\\u00db');
+    });
+  });
 });