Ambiguious Custom model fallback option for OpenCode

**Motivation**
I've set an OpenCode agent to run on a non-existing custom model (to my knowledge).
In theory it should not be able to run, or work at all, but it did.

**Proposed solution**
There should be a label or something to show which model is the agent actually running on.

**Alternatives considered**
Shows fail to load model and fail to start agent

**Additional context**