feat: optimized sparse embedding interface

Makefile

docs/encoders/aurelio-bm25.ipynb

docs/examples/hybrid-router.ipynb

docs/examples/pinecone-hybrid.ipynb

semantic_router/encoders/aurelio.py

semantic_router/encoders/base.py

semantic_router/encoders/tfidf.py

semantic_router/index/hybrid_local.py

semantic_router/index/pinecone.py

semantic_router/routers/base.py

semantic_router/routers/hybrid.py

semantic_router/routers/semantic.py

semantic_router/schema.py

tests/unit/test_sync.py