## What changed
- Add the built-in `amazon-bedrock-runtime` provider for regional
`bedrock-runtime` OpenAI-compatible endpoints.
- Use endpoint-specific SigV4 service configuration while preserving bearer
token auth and per-provider AWS profile, region, and transport overrides.
- Provide global and US cross-region GPT-5.6 model variants, prefer global
routing for fallback and background tasks, and disable unsupported web search.
## Testing
- Cover provider configuration and capabilities, endpoint and auth selection,
runtime catalog ordering, model fallback, and web search omission.
GitOrigin-RevId: d158ab74a5768e1b4c61063365a0c06735313322