Add native SAP AI Core provider that handles OAuth token management and
deployment discovery automatically. This eliminates the need for the
external LLM proxy when running in SAP environments.
Changes:
- Add AICoreClient with OAuth token caching and deployment URL discovery
- Support both Anthropic and OpenAI models via AI Core deployments
- Update CI to use native AI Core provider
- Update action inputs to accept AI Core credentials
- Update README with AI Core configuration examples
Model names must match AI Core deployment names (e.g. anthropic--claude-4.6-sonnet, gpt-5).
Rodin