Changes
PR #2241 by ksylvan: fix: require explicit configuration for optional-key AI providers
- Fixed optional-key AI providers so they now require explicit configuration before activation.
- Required base URL environment variables for providers that do not need an API key.
- Preserved existing configuration checks for providers that require an API key.
- Added tests covering optional-key activation and required-key checks without credentials.
- Documented Apple Foundation Models activation through
fabric -S.