At document start (where the app installs the X runtime) there is no <html> element yet, so
the lang report never ran and "Follow X" never learned X's language (found live: siteLang
stayed null). It now reads lang again at readystatechange/DOMContentLoaded, and a report
that fails (no bridge yet) is retried with a bounded backoff. Tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
