[Feature]: Agent selection and model selection with OpenCode

### Problem or use case

As of now, the only way to use a specific agent to execute a task is to write a custom command to launch the OpenCode CLI. The same goes for model selection, as I have a subscription for OpenCode Go, I like to switch them depending on the task.

### Proposed solution

Be able to pick a specific OpenCode agent for a task and/or select the model amongst the ones available before executing a task.

### Alternatives or additional context

_No response_