fix(test): vendor CodeMirror 6 bundle so richtext tests don't depend on esm.sh

The CodeMirror 6 rich-text fixture imported codemirror@6.0.1 from esm.sh,
which fans out to the entire @codemirror/* + @lezer/* module graph over many
serial requests. In CI this reliably exceeded the 30s waitForFunction timeout,
so window.__editorReady never became true and all four CodeMirror 6 fillField
tests timed out across Playwright, Puppeteer and WebDriver. Pre-existing on 4.x
and unrelated to the junit change on this branch.

Vendor the self-contained esm.sh bundle locally and import it same-origin,
making the test network-independent and deterministic. Exclude the vendored
blob from eslint and prettier.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: DavertMik

.prettierignore

@@ -0,0 +1,2 @@
+# Vendored third-party bundles used by rich-text editor test fixtures
+test/data/app/js/

eslint.config.mjs

@@ -14,7 +14,7 @@ const compat = new FlatCompat({
 
 export default [
   {
-    ignores: ['test/data/output', 'lib/css2xpath/*'],
+    ignores: ['test/data/output', 'test/data/app/js/*', 'lib/css2xpath/*'],
   },
   {
     languageOptions: {

test/data/app/js/codemirror6.js

@@ -14,7 +14,7 @@
         <button type="submit" id="submit">Submit</button>
     </form>
     <script type="module">
-        import { EditorView, minimalSetup } from 'https://esm.sh/codemirror@6.0.1'
+        import { EditorView, minimalSetup } from '/js/codemirror6.js'
         const initial = <?php echo json_encode($initial, JSON_UNESCAPED_UNICODE); ?>;
         const view = new EditorView({
             doc: initial,