Address the "recognized but marker left raw" cases from the audit, plus code syntax colors: - Headings: hide the optional closing `##` sequence, not just the opening. - Escapes / hard breaks (new escapeDecoration.ts): hide the backslash of `\x` escapes and the `\` hard-line-break form, so the escaped character renders literally. - Reference links: hide the `[ref]` label (no URL child) and mute the `[ref]: url` definition line via cm-link-def. - Fenced code: hide the language label (CodeInfo) off-block so no stray `js` floats above the box. - Code syntax colors: add a scoped tok-* palette (light + data-theme dark) so classHighlighter output is actually colored. - Nested blockquotes: cm-quote-{depth} by `>` count per line, with progressive indent/bar instead of flat styling. Extends the headless builder tests with a case per fix (146 passing). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>