[FEATURE]: Deeplink support for web UI #6847

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

My use case
I use opencode in web browser and write code in my code editor. I would like opencode web UI to support deeplinks that would redirect me back to my code editor when clicked. I often find myself asking LLM to explain how to achieve something I want instead of asking it to implement it. I would want the markdown returned by LLM to render links that link back to my code editor.

Possible implementation
We could have marked.js extension that detects filenames and intelligently renders them as href to a deeplink if it is configured. However, Im not sure where and in what form deeplink template should be configured, I assume it should be in opencode.jsonc.