Agents folder setting support

### Describe the feature or problem you'd like to solve

Setting for custom agents folders or sub-folders.

### Proposed solution

VS code and copilot chat has syntax like the following:
```json
"chat.agentFilesLocations": {
".github/agents/atlas": true
}
```

It would be either good to read the same settings file and setting or create similar feature, so that agent orchestrators with their list of sub-agents could be kept in separate folders.

E.g. sub-agent naming might not follow the main agent naming and if trying out several agent orchestrators in same repo (or even user folder), especially sub-agents get messy to separate and maintain. If files would be renamed in orchestrator repo, copy-pasting an orchestrator to your repo and keeping things clean becomes even harder.

### Example prompts or workflows

_No response_

### Additional context

_No response_