Render Markdown links as clickable labels in supported terminals (#40471)

## What changed

- Render web-link labels in cyan with an underline and hide the repeated destination in recognized terminals with hyperlink support.
- Keep destinations visible for unknown terminals, multiplexers, non-terminal output, and empty labels so the URL remains usable.
- Preserve OSC 8 link targets through prose and table wrapping, streaming updates, transcript clipping, and pager scrolling.

## Testing

- Add coverage for terminal detection, label formatting and fallbacks, wrapped tables and prose, streaming parity, history output, and scrolled transcript rendering.

GitOrigin-RevId: 4a09e41e349ba299022a9c00f0c25892d9aaefe3

codex-rs/tui/src/chatwidget.rs

@@ -171,7 +171,6 @@ use ratatui::style::Modifier;
 use ratatui::style::Style;
 use ratatui::style::Stylize;
 use ratatui::text::Line;
-use ratatui::text::Text;
 use ratatui::widgets::Clear;
 use ratatui::widgets::Paragraph;
 use ratatui::widgets::Widget;