Eliminate the smartSentenceSplitting configuration flag from application state, UI, and all TTS and audiobook adapter logic. Consolidate TTS segment planning to always include context units, streamlining code and reducing conditional branches. Update tests and type definitions to reflect the removal of this feature toggle.
Introduce sentence and word highlighting for HTML/TXT/MD documents, including new config options (`htmlHighlightEnabled`, `htmlWordHighlightEnabled`) and synced user preferences. Update the HTML viewer to support these highlights using custom spans, and add corresponding CSS styles. Extend document settings to allow toggling these features. Implement block-level locator sorting and display improvements. Add audiobook export support for HTML documents, including adapter and pipeline integration.
- Add `htmlHighlightEnabled` and `htmlWordHighlightEnabled` to config, user state, and Dexie storage
- Update HTML viewer to apply and manage highlights for sentences and words
- Add CSS for HTML highlight classes and scroll margin
- Extend document settings UI for HTML highlight toggles
- Support HTML audiobook export in modal and pipeline
- Improve block locator sorting and sidebar display for HTML
- Add HTML audiobook adapter and block parsing utilities
