[Feature]: Allow setting a fixed model for builtin agents without needing the override the whole agent

[bvolkmer]

1. Why Do You NEED This Feature?

I want muse to use a more powerful model than forge and do not want to type in two commands for agent switching every time.

2. What Is NOT Possible Right Now?

Currently, the only way to set specific models per builtin agent, requires overwriting the whole agent. This is bad because in case of an update the agent does not get updated, as it is overwritten.

3. What WILL Be Possible With This Feature?

Set a model per agent without needing to overwrite it.

Proposed Solution (User Experience)

An option to set the model per agent without needing to touch the model definition.

Alternatives Considered

No response

Feature Category

Configuration

Priority/Impact

Medium - Would be nice to have

Examples from Other Tools

No response

Additional Context

No response

Pre-submission Checklist

• I have searched existing issues and confirmed this is not a duplicate
• I am willing to submit a PR to implement this feature