feat(ai): add Hugging Face provider support

- Add huggingface to KnownProvider type
- Add HF_TOKEN env var mapping
- Process huggingface models from models.dev (14 models)
- Use openai-completions API with compat settings
- Add tests for all provider test suites
- Update documentation

fixes #994

packages/ai/src/env-api-keys.ts

@@ -105,6 +105,7 @@ export function getEnvApiKey(provider: any): string | undefined {
 		mistral: "MISTRAL_API_KEY",
 		minimax: "MINIMAX_API_KEY",
 		"minimax-cn": "MINIMAX_CN_API_KEY",
+		huggingface: "HF_TOKEN",
 		opencode: "OPENCODE_API_KEY",
 	};