Evidence attribution accuracy tests #4

Description

Search answers are supposed to point back to the exact passage they came from. We need to verify attributions are actually correct, not just present.

Proposed Solution

Build tests that check returned citations point to the passage that genuinely supports the answer, using labeled query/answer/citation examples.

Acceptance Criteria

• Labeled examples of query, answer, and correct citation exist
• Tests verify citations point to the correct source passage
• Tests flag cases where an answer has no valid supporting citation
• Results are reproducible and comparable across runs