Bug: composing duplicate queries throws an error

[kbolashev]

To reproduce:

# Assuming there's a ds already
ds2 = ds["x"] > 5
ds3 = (ds2["y"] < 10) | (ds2["y"] > 20)

Before this PR, doing something like this threw a DuplicateKeyError.
Solving this by doing a deep copy of the operand tree of composed trees every time.

[dagshub]

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[Copilot]

Pull Request Overview

This PR fixes a bug where composing queries with duplicate subqueries would throw a DuplicateKeyError due to node identifier conflicts in the query tree structure. The solution implements deep cloning of operand trees with unique identifiers to prevent conflicts when the same subquery is reused.

Key changes:

• Added deep cloning functionality to prevent node identifier conflicts in query composition
• Implemented comprehensive test coverage for the duplicate subquery scenario

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
dagshub/data_engine/model/query.py	Adds deep cloning logic with UUID-based node identifiers to resolve duplicate key conflicts
tests/data_engine/test_querying.py	Adds test case reproducing and validating the fix for duplicate subquery composition