[BUG] Windows desktop: a `:N` line suffix on a markdown-file link silently kills the link, while the same suffix works on code files

What's Wrong?

On the Windows desktop app (2.1.219), a relative markdown link to a .md file opens correctly — until a line-number suffix is added, at which point the click is silently dropped. The identical suffix works on a code file.

Tested in one session, same pane, same project, four link forms:

| Link form | Result |
|---|---|
| [notes.md](notes.md) | ✅ opens, at top |
| [notes.md:9](notes.md:9) | ❌ click does nothing at all |
| [notes.md#some-heading](notes.md#some-heading) | ✅ opens, anchor ignored — lands at top |
| [script.py:479](src/script.py:479) | ✅ opens at line 479 |

So the :N form is supported (code files honour it precisely), and .md links are supported (they open), but the combination fails closed rather than degrading.

Why this one bites harder than it looks: Claude Code's own guidance tells the model to emit file references as path/to/file.md:42 markdown links because they're clickable. For .md targets that instruction produces a dead link every time — and because the styling still looks clickable, neither the model nor the user gets any signal it failed.

What Should Happen?

A .md link with a :N suffix should open the file — at that line if the preview supports it, at the top if not. Degrade, don't drop. Ideally #heading anchors would scroll the markdown preview to the heading too, but the silent failure is the actual bug.

Environment

Windows 11, Claude Code desktop app 2.1.219.

Related, not duplicate

• #81817 (absolute-path hrefs dropped on Windows desktop — ours are relative and work without the suffix)
• #73417 (heading anchors in the VSCode extension)