GitHub Copilot provider lists unavailable models instead of org-enabled ones

[amaduswaray]

Description When using GitHub Copilot as the model provider, OpenCode lists all models exposed by Copilot, rather than only the models that are enabled for the current organization.

As a result, the UI shows models that cannot actually be used by the user.

Problem There is currently no way to know whether a selected model is available until a request is made. If the model is not enabled for the organization, the request fails at runtime.

This makes it difficult to:

• Know which models are usable
• Understand organization-level Copilot restrictions