ModelScope is a fully implemented provider (nanobot/providers/registry.py,
image_generation.py, schema.py) with async image-generation task submission
and polling, but was previously undocumented in docs/providers.md.
This patch adds a ModelScope entry under 'Common Provider Patterns',
covering:
- Default base URL: https://api-inference.modelscope.cn/v1
- OpenAI-compatible chat/completions endpoint
- Async image-generation flow (task submit + status poll)
- Automatic 'modelscope/' prefix stripping when calling the API
- A minimal nanobot.yaml example
No code changes; docs-only.
