## Why
Overflowing whitespace in the TUI composer could occupy a separate blank row
instead of remaining attached to the text that follows it.
## What changed
- Add composer-specific, grapheme-safe wrapping that keeps breakable Unicode
whitespace with the following word while preserving semantic breakpoints such
as hyphens and nonbreaking spaces.
- Preserve cursor insertion rows and positions as content reflows, including
across full lines and wrapped fragments.
- Keep wrapping linear for maximum-length unbroken input.
## Testing
Add focused rendering and cursor tests for ASCII and Unicode whitespace,
hyphenated words, reflowed fragments, and maximum-length input.
GitOrigin-RevId: fb7713e33bfddf37460b6c2f6f0c9700f31d86bf
Charlie Marsh
a16863f870