fix: reject duplicate notes from get_notes

[AztecBot]

Summary

get_notes validated each hinted note independently, so a malicious witness could return the same note multiple times in one call. This change rejects duplicate note existence requests during hint confirmation, which is the narrow fix for preventing duplicated returned notes.

Fix

• Track each confirmed (note_hash, contract_address) pair while confirming hinted notes and reject repeats.
• Add a focused regression that constructs duplicate valid hinted notes and expects confirmation to fail.

Testing

• ../../noir/noir-repo/target/debug/nargo test --package noir_aztec --exact note::note_getter::test::confirm_notes_rejects_duplicate_hinted_note --silence-warnings --test-threads 1 failed before the fix with Test passed when it should have failed
• ../../noir/noir-repo/target/debug/nargo test --package noir_aztec --exact note::note_getter::test::confirm_notes_rejects_duplicate_hinted_note --silence-warnings --test-threads 1
• ../../noir/noir-repo/target/debug/nargo fmt --package noir_aztec
• ../../noir/noir-repo/target/debug/nargo test --package noir_aztec --no-run --silence-warnings
• git diff --check

Issues

• Closes AztecProtocol/aztec-claude#982 — get_notes can return one note multiple times

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Created by claudebox · group: kernels-audit-remediation