Optimize highlight.rs to only produce markers for visible lines
Reduce memory usage by accepting a line range parameter in extract_highlights()
and only producing style markers for lines that will be displayed in the code
frame. This is especially beneficial for large files where only ~10-20 lines
are visible.
Changes:
- Add Range<usize> parameter to extract_highlights() for 0-indexed line ranges
- Add byte-range filtering to skip marker production outside visible range
- Still lex entire file to maintain correct parsing state
- Update frame.rs to pass first_line..last_line range
- Add tests for line range filtering and marker count reduction
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
