Polish: npm test runs every test file, two silent failures now log, Loading placeholders shimmer

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/file-history.js

@@ -2,7 +2,7 @@
 // Uses sf, fmtSize, openSheet, confirmSheet, toast, esc and FORM from app.js.
 async function fileHistory(repo, path, name, readOnly) {
   const base = `/api2/repos/${encodeURIComponent(repo)}/file`;
-  const el = openSheet('Version history', name, '<p class="empty">Loading…</p>');
+  const el = openSheet('Version history', name, '<p class="empty loading" role="status">Loading…</p>');
   el.querySelector('.sheet').classList.add('wide');
   try {
     let commits = [], next = '';