fix(app): file:// links in chat render broken, so PDF paths aren't clickable #383

What happened

In an Amicode chat, I gave two clickable PDF links written as markdown file:///... URLs. The chat UI rendered them broken, so they could not be opened from the chat panel. Plain text paths were not clickable either.

Expected

Local file references in assistant messages should be clickable (open in the viewer or the OS), or at least render as readable absolute paths.

Repro

1. Ask the assistant to show a link to a local PDF.
2. The assistant writes [name](file:///home/.../file.pdf).
3. Click it in the chat panel: the link is broken.

Workaround

Use absolute paths or GitHub URLs in messages.

Context

Seen in the QuEra proposal campaign (session-20261105-quera-pilot-proposal), 2026-11-05.