Polish _clean_title for R-F: strip accent/escape macros (backslash-quote o to o, backslash-amp), convert tilde ties to spaces, and truncate at a word boundary so stored section titles read cleanly (mobius invariance, colin de verdiere). Tests added; ruff + mypy clean. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>