Remove the per-provider listModels API (GET /providers/:id/models) and all
four provider implementations (OpenAI Compatible, OpenAI Responses, Anthropic,
Gemini). ModelCombobox now only shows tokenlens suggestions (tagged '推荐') plus
free-form custom input — no more unfiltered 'API' models from provider SDKs.
Fixes: switching provider type in ProviderDialog no longer shows stale models
from the original provider's API.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Component tests for all LLM management UI elements using vitest and
@testing-library/react with happy-dom:
- LLMProviders: Tab container rendering
- ModelCombobox: API/recommended/custom tag display, selection, custom input
- ProviderList: Async data loading, enable switches, status indicators
- RoleAssignment: Role card rendering, Radix Select interaction
- TestResultDialog: Success/error state rendering
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
