Windows desktop: file card path in chat attachment box drops backslashes

<img width="1409" height="1116" alt="Image" src="https://github.com/user-attachments/assets/36ed39b9-4946-49d7-82c3-e02c077900f2" />

Summary

When the assistant references a local file in a reply, the black file card sometimes shows a malformed Windows path with missing slashes (for example C:Projectsnew-pc-dev-setupdocs16-day0-quick-start.md) instead of a normal file label/path.

Expected behavior

• File card should show a clean filename (for example 16-day0-quick-start.md)
• If full path is shown, slashes should be preserved correctly (for example C:\Projects\new-pc-dev-setup\docs\16-day0-quick-start.md)

Actual behavior

• File card shows malformed path with stripped separators.

Repro steps

1. In Codex desktop app, ask assistant to reference a local file using a Windows absolute path markdown link.
2. Assistant responds with file link.
3. Observe black file card at bottom of assistant message.
4. Path text appears concatenated (missing \\).

Environment

• Codex desktop app
• Windows 11
• Reproducible in normal conversation replies with file references

Impact

• Confusing file identity/path display
• Looks broken and reduces trust in file-linking UI
• and the link fails see attached file

<img width="103" height="96" alt="Image" src="https://github.com/user-attachments/assets/66534507-6ed7-4f79-a0d2-b66a28790896" />

• Open as action also fails (no file is opened)

Note

I have a screenshot and can attach it if needed.