Syntax highlighting bug fixes

[waf]

• Handle when newline has syntax highlighting applied to it (typically when the newline is inside a syntax-highlighted string)
• Handle mismatched coloring when grapheme clusters are not exactly one char wide / one column wide

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.5%. Comparing base (132bb39) to head (de6d825).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/PrettyPrompt/Highlighting/CellRenderer.cs	88.2%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #290   +/-   ##
=====================================
  Coverage   84.4%   84.5%           
=====================================
  Files         47      47           
  Lines       3947    3950    +3     
  Branches     655     658    +3     
=====================================
+ Hits        3335    3340    +5     
+ Misses       454     450    -4     
- Partials     158     160    +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.