feat: show link text next to the URL in link-hint mode

[borghei]

Summary

Closes #8.

The f link-hint popup listed only URLs, so it was hard to tell which entry matched which link in the document. Each row now shows the link's text next to its URL:

│  a  ink project documentation on the web  https://example.com/docs/getting-started/installati… │
│  b  https://x.y                                                                                │
│  c  bold and italic link  https://example.com/b                                                │

• The caption is the text of the link's consecutive spans, joined across a line wrap.
• Autolinks, bare URLs and mailto: addresses keep the old single-column row, so a URL is never printed twice.
• The popup grows from 60 up to 100 columns to fit. When a row is still too long the caption is shortened first, then the URL. Widths are measured in terminal cells, so wide glyphs cannot overflow.
• The Y copy-URL variant shares the same rows.

Testing

• 12 new unit tests: caption collection, multi-span and wrapped captions, autolink suppression, dedupe by URL, the a..z cap, a real laid-out markdown snippet, and the row-fitting function.
• cargo fmt, cargo clippy --all-targets -- -D warnings, cargo test pass locally.
• Verified in a pty at 100x30: f and f then Y both show captions.

🤖 Generated with Claude Code

https://claude.ai/code/session_01UVcvmQrSXd2eyt32g4ko19