[FEATURE]: add D.Run (China) provider support #16604
Description
Feature hasn't been suggested before.
- I have verified this feature I'm about to request hasn't been suggested before.
Describe the enhancement you want to request
D.Run is a cloud AI inference platform from DaoCloud, providing OpenAI-compatible API access.
The models.dev definition has been merged: anomalyco/models.dev#1083
This issue tracks the opencode-side registration (CUSTOM_LOADERS entry + provider logo).