improved --path handling in CLI #64 fix ef and dim selection #65

[iQuxLE]

Not including --path when indexing cause a downstream error for the DuckDB implementation.
This handles the cases better as discussed in #64

• resolves seems to be using duckdb even when chromadb is requested (indexing JSON) #64

Updating vocab, get_ef and get_embedding_dimension

• resolves embedding dimension and function do not provide correct values #65