Review unnecessary cloning in HNSW search

[mmailhos]

There are multiple .clone() calls that could be optimized:

// Lines 333-342 (during deserialization)
hnsw.insert(values.clone(), searcher)

// Lines 374-383 (during add operation)
hnsw.insert(vector.values.clone(), searcher)

// Lines 508-510 (during get_vector)
values: values.clone(),
text: meta.text.clone(),
metadata: meta.metadata.clone(),

Considerations:

• Use Arc<Vec<f64>> for shared vector values
• Use Arc<String> for text
• Consider Arc<serde_json::Value> for metadata
• Can HNSW library accepts references instead of owned values?