[201_103] Fix #2324: Normalize URLs in \slink navigation

[Prthmsh7]

Fixes #2324

After:

Screen.Recording.2026-03-30.at.1.14.56.PM.mov

What

• Added runtime URL normalization for \slink
• Introduced slink-url-normalize and integrated it into go-to-url
• Reverted earlier markup-layer approach to preserve TeXmacs tree structure

Why

• URLs without a scheme (e.g., liiistem.cn) were treated as local file paths
• This caused navigation to fail when using \slink
• Applying normalization at the markup layer broke link behavior by altering the document structure

How

• Implemented a heuristic that:
  • Detects missing schemes (://)
  • Identifies domain-like strings (contains .)
  • Skips local paths (/, ~)
• Applied normalization in the navigation layer before URL resolution

[Prthmsh7]

@Yuki-Nagori Could you please review this as well when you have a moment? Thanks!

[Yuki-Nagori]

The functionality is implemented, but a judgment for whether it is a file needs to be added. Otherwise, if "test.pdf" is entered, it would originally open the file, but now it is being judged as a URL.

Before After