fix: ensure nullable binary arrays return boxed type arrays instead of Object[]

[kishansinghifs1]

Summary

BinaryStreamReader.readArrayItem used Object.class as the element type for all nullable array columns, so Array(Nullable(Float64)) returned Object[] instead of Double[]. This splits the nullable check from the Variant/Dynamic/Geometry fallback and derives the correct boxed wrapper class via getObjectClass(). Added unit test to verify the component type is Double.class for Array(Nullable(Float64)).

Closes : #2846

Checklist

Delete items not relevant to your PR:

• Closes BinaryStreamReader.ArrayValue wrong return type #2846
• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

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[chernser]

@kishansinghifs1

Thank you for the contribution!

I will review next week.

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Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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Empty nullable array typing

Medium Severity

When a nullable array has length zero, readArray still uses getPrimitiveClass (e.g. double for Float64) instead of the boxed types used in readArrayItem. The same column can yield primitive empty arrays but boxed non-empty arrays.

 

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[kishansinghifs1]

Hiii @chernser,
thank you for the opportunity ,
no worries.