fix: support unhashable metadata comparison values in recall and NDCG evaluators

[CoralGarden52]

Related Issues

No existing issue was found for this behavior.

Proposed Changes

Document.meta supports JSON-serializable values, including lists and dictionaries.
However, when document_comparison_field points to such a value:

• DocumentRecallEvaluator raises TypeError because it stores comparison values in a set.
• DocumentNDCGEvaluator raises TypeError because it uses comparison values as dictionary keys.

This is inconsistent with DocumentMAPEvaluator, which already supports unhashable comparison values.

This change adds a shared internal helper that converts nested list, tuple, and dictionary values into hashable representations while preserving their comparison semantics:

• list and tuple order is preserved;
• dictionary key insertion order is ignored;
• nested containers are supported;
• composite values are compared as complete values, not as element intersections.

Existing deduplication behavior is preserved:

• Recall counts each unique comparison value once.
• NDCG keeps the highest relevance score for duplicate ground-truth values.
• Duplicate retrieved values are credited only once.

How did you test it?

• Added regression tests for list and dictionary metadata values.
• Added tests for nested values and list ordering.
• Added tests for duplicate values and NDCG relevance-score handling.
• Target evaluator tests: 110 passed.
• Evaluator tests excluding the optional SAS evaluator: 175 passed, 4 skipped.
• Ran Ruff, mypy, Reno lint, and pre-commit successfully.
• SAS model-backed integration tests were intentionally not run because they require model weights.

Notes for the reviewer

The implementation follows the duplicate-value semantics introduced by
#12255 and
#11959.

This is an internal implementation change with no public API changes.

This PR was fully generated with an AI assistant. The changes have been reviewed and the relevant tests have been run.

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