Option to pull all model information live

Goal: Goose should have an option to pull all model information (context limits, modalities) from a live source instead of the existing pre-built canonical_models.json. You shouldn't need to update goose to get support for a new model's canonical info. (There still may be updates required for new models as they may include API changes, but that is not always the case.)

Some options:
- pull directly from models.dev live
- pull a live version of our existing canonical_models.json
- shift to querying all of this directly from providers

Look for the canonical_models.json file and the code that loads it, likely in a config or models module. Understand how model information (context limits, modalities) is currently used. Investigate the suggested live sources: models.dev or provider APIs. Determine how to add a configuration option to switch between static and live fetching, and ensure error handling for network failures.

Escrito por el modelo de indexación a partir del texto del issue.