fix: remove embedding vector from Milvus search output_fields

[octo-patch]

Fixes #238

Problem

In some Milvus configurations (e.g. Milvus docker standalone, Milvus server deployments), requesting the embedding vector field as an output field in client.search() raises:

MilvusException: (code=65535, message=field embedding not exist)

This causes search_data() to fail entirely, making the whole query pipeline crash with a RuntimeError.

Root Cause

The output_fields=["embedding", "text", "reference", "metadata"] parameter requests the dense vector field back from Milvus. Some Milvus versions or server configurations do not support returning vector fields via output_fields, resulting in the above exception.

Importantly, RetrievalResult.embedding is never used downstream — it only appears in __repr__(). No agent code reads the embedding from search results, making this retrieval unnecessary and wasteful (embeddings can be thousands of floats per result).

Solution

• Remove "embedding" from output_fields in both regular search and hybrid search calls
• Pass None for the embedding parameter when constructing RetrievalResult

This eliminates the exception, reduces data transfer from Milvus, and has no functional impact since the embedding value from search results is never consumed.

Testing

Verified against existing tests/vector_db/test_milvus.py test suite — test_search_data passes as before since it only checks the result is a RetrievalResult instance, not its embedding value.

[sre-ci-robot]

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