Tests with _=\"...\" attribute delimiters were garbled because
HTMLParser interpreted the backslash-quote as content, not delimiters.
Now html.replace('\"', '"') normalizes before parsing.
Fixes ~15 tests across toggle, transition, and other categories
that were previously running with corrupted HS source.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>