bug: DiskANN CalcDistByIDs returns incorrect COSINE/IP distances when all vectors are cached

[SpadeA-Tang]

DiskANN CalcDistByIDs returns early when all requested vectors are found in the coordinate cache, skipping the metric-specific distance
conversion.

As a result:

• COSINE similarity is returned with the wrong sign.
• INNER_PRODUCT conversion and norm rescaling are skipped.
• L2 and requests containing uncached vectors are unaffected.

[github-actions]

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