Terminal output: clickable web links

### Problem

URLs printed in the task terminal are plain text today. To open one, you have to select the text, copy it, and paste it into a browser — for every link, every time.

### Desired outcome

Links in terminal output are recognizable and clickable: hover/click opens the URL in the system browser. For safety, only explicit `http:` / `https:` URLs should be openable — non-web schemes (e.g. `file:`, custom app schemes) and malformed values should be ignored. The main-process external-link guard should remain the final boundary behind `window.open`.

### Alternatives or workarounds

Manually copying the URL from the terminal into a browser.