Add support for model configuration editing with Mira

[brandomr]

This implements a new context called mira_config_edit which fetches a model configuration from HMI server on setup, lets the user ask for 3 basic things:

1. what are the current parameters?
2. what are the current initial conditions?
3. update the parameter values

It accepts a custom message called save_model_config_request which does a PUT to update the model configuration in place.

No actions except for loading/saving the configuration occur "behind the scenes". For the 3 items above Beaker generates code that the user must then confirm and execute. The user is not constrained in this environment and can make freeform edits to the model configuration beyond those supported by the LLM.

Note: the env.example is now updated to support HMI-Server URL and auth information.

Questions

1. Should this create a new configuration or overwrite the existing one?
2. Does any provenance information need to be stored?
3. Should initial condition expressions be editable via LLM support?