feat: further docstrings and cleanup

semantic_router/encoders/cohere.py

semantic_router/encoders/fastembed.py

semantic_router/encoders/google.py

semantic_router/encoders/huggingface.py

semantic_router/encoders/mistral.py

semantic_router/encoders/openai.py

semantic_router/encoders/vit.py

semantic_router/encoders/zure.py

semantic_router/linear.py

semantic_router/llms/base.py

semantic_router/llms/cohere.py

semantic_router/llms/llamacpp.py

semantic_router/llms/mistral.py

semantic_router/llms/ollama.py

semantic_router/llms/openai.py

semantic_router/llms/openrouter.py

semantic_router/llms/zure.py

semantic_router/route.py

semantic_router/schema.py

semantic_router/utils/defaults.py