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

I have a mono repo and I often start opencode accidentally from a sub directory. Due to sandboxing, the agent does not have access to the agents.md file and therefore is not aware of my preferences or even code that would be relevant to the task at hand.

I would really like opencode to let me know when I'm trying to use an agent that does not have access to my agents.md whether it's due to sandboxing or because initialization has not been done.

If it is actually easy to set the context to the repo root when starting from a subfolder, I have not found it in the documentation.

I'm mainly talking about the UX, I would really want a message/warning light that the agent is flying blind.

There are some other issues that mention similar issues, afaict the most relevant are
#1143
#1877
#2177