Refactor EPUB and HTML word highlighting to use a shared, position-preserving
text normalization pipeline for mapping TTS alignment offsets to DOM positions.
Replace the previous fuzzy token-matching logic with a direct char→DOM map
based on the canonical "audio" text form, ensuring highlights stay in sync
across languages and with Unicode-aware hyphenation handling.
- Add `highlight-char-map.ts` for shared normalization logic
- Update normalization to handle Unicode hyphenation consistently across
compute, client, and shared layers
- Remove unused fuzzy token mapping and cache logic from EPUB highlighting
- Update tests for new highlight mapping and normalization behavior
BREAKING CHANGE: Removes legacy fuzzy token-based word highlight mapping in favor of direct char offset mapping; highlight cache and tokenization APIs are removed.
