Why this change is needed:
To support vector storage model isolation, we need to track which model is used for embeddings and generate unique identifiers for collections/tables.
How it solves it:
- Added model_name field to EmbeddingFunc
- Added get_model_identifier() method to generate sanitized suffix
- Added unit tests to verify behavior
Impact:
Enables subsequent changes in storage backends to isolate data by model.
Testing:
Added tests/test_embedding_func.py passing.
