### What problem does this PR solve?
Support model list for VolcEngine.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
This PR adds `ModelMeta` implementations for four additional LLM/RAG
ecosystem platforms, building on the ModelMeta infrastructure introduced
in #15711.
Currently, only `Ollama` and `VolcEngine` have `ModelMeta` classes that
enable remote model list fetching. This PR extends that support to four
more platforms.
### Changes
Added four new `ModelMeta` subclasses in `rag/llm/model_meta.py`:
| Platform | `_FACTORY_NAME` | Has model list | Has full model info |
Approach |
|----------|-----------------|----------------|---------------------|----------|
| **Xinference** | `"Xinference"` | ✅ | ✅ | Parses `model_type` and
`context_length` from `/v1/models` response. Maps 6 model types
(LLM/embedding/rerank/image/TTS/speech2text). |
| **LocalAI** | `"LocalAI"` | ✅ | ✅ | Uses Ollama-compatible `GET
/api/tags` + `POST /api/show` endpoints. Returns capabilities
(completion/embedding/vision/tools/thinking) and
`general.context_length`. |
| **BaiduYiyan** | `"BaiduYiyan"` | ✅ | ✅ | Uses Qianfan SDK static
model catalog + `get_model_info()` for `max_input_tokens`. Returns 60
models (56 chat + 4 embedding) with real context lengths. |
| **Tencent Cloud** | `"Tencent Cloud"` | ❌ | ❌ | `NotImplementedError`
— uses SDK-based SID/SK HMAC signing, no model list REST API available.
|
All classes are automatically discovered and registered via the existing
`__init__.py` mechanism — no additional configuration needed.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat：
- Get model list from remote provider.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
