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"]
}

从 ~/.commandcode/providers.json 所表示的用户范围配置开始，然后跟踪 /model 菜单和模型选择快捷键。检查内置模型 ID 和提供商级别的禁用设置是如何加载和过滤的。完成的标准是：用户可以跨项目禁用选定的内置模型，同时现有的 BYOK 提供商行为保持不变。