* fix: improve model configuration for litellm gateway
* fix: add missing config imports for Cohere and LiteLLM providers
Add missing DEFAULT_* and ENV_* constants to cross_encoder.py and embeddings.py imports:
- DEFAULT_RERANKER_COHERE_MODEL
- DEFAULT_LITELLM_API_BASE
- DEFAULT_RERANKER_LITELLM_MODEL
- DEFAULT_EMBEDDINGS_COHERE_MODEL
- DEFAULT_EMBEDDINGS_LITELLM_MODEL
- ENV_RERANKER_COHERE_MODEL
This fixes NameError failures in test-api, test-hindsight-all, and test-upgrade CI jobs.