fix(tui): buffer terminal frame output

[larsch]

Summary

Interactive mode could render screen updates one character at a time when the system was under load, particularly on Windows.

The Ratatui Crossterm backend was writing directly to stderr, so its per-cell terminal commands were not buffered before being sent to the terminal. This made intermediate frame output visible during rendering.

This change wraps the TUI’s stderr writer in io::BufWriter. Ratatui still flushes the backend after each completed frame, preserving timely updates while ensuring frame output is written in larger batches.

Verification

• cargo fmt --check
• cargo check
• cargo test --lib
• Manually verified on Windows under load; significant improvement observed.
• Manually verified on Linux under load; significant improvement observed.

[Byron]

Thanks so much!

I tried this on Windows and that fixes the sluggishness!
I always thought that's just how it is on Windows 😅.

[Byron]

And it's released.