Support vectors in Rfile and from accumulo clients #2
Description
Add vector-typed Values (ValueType.VECTOR_FLOAT32).
Extend RFile.Writer to allow writing contiguous vector blocks with metadata.
In RFile.Reader, allow optional VectorIndex section per block.
Provide a new VectorIterator that:
Takes a query vector
Traverses block centroids (coarse filter??)
Reads candidate vectors + computes similarity (cosine/dot product)
Applies VisibilityEvaluator before returning results.