Allow disabling individual built-in models

Feature request

I'd like to be able to disable individual built-in Command Code models from the /model menu.

Right now, ~/.commandcode/providers.json supports disabling an entire BYOK provider with "disabled": true, but there doesn't seem to be a supported way to hide or disable one specific built-in model.

I'd like a configuration option at user scope that lets me disable specific models without removing access to the rest of the catalog. This would make the model picker less cluttered and make it easier to prevent accidental selection of models I don't want to use.

Suggested behavior

• Support an allowlist or denylist for built-in model IDs.
• Apply it to the /model menu and model selection shortcuts.
• Keep the setting at user scope so it applies across projects.
• Keep the current BYOK provider-level disabled behavior unchanged.

Example

{
  "disabledModels": ["some/model-id"]
}

Start with the user-scope configuration represented by ~/.commandcode/providers.json, then trace the /model menu and model-selection shortcuts. Check how built-in model IDs and provider-level disabled settings are loaded and filtered. Done means a user can disable selected built-in models across projects while the existing BYOK provider behavior remains unchanged.