[2.0] Add DuckDB final verification gate

[joyemang33]

Summary

• Add a final-only DuckDB SQLLogicTest smoke gate for the DuckDB E2E query optimization task.
• Split iterative async feedback from final scoring: async submissions run the public-scale TPC-H gate, while final verification runs the broader scale-factor set plus SQLLogicTest smoke.
• Make best async submission reuse go through a verifier-only final rerun instead of falling back to an old async score record.

Please read CONTRIBUTING.md before submitting.

Type of Change

• New research problem
• New algorithmic problem
• New Frontier-CS 2.0 problem
• Bug fix
• Documentation update
• Other:

Testing

• python3 -m py_compile 2.0/problems/duckdb_e2e_query_optimization/evaluator.py adapters/frontier-cs-2.0/src/frontier_cs_2_0/task-template/environment/judge_server.py adapters/frontier-cs-2.0/src/frontier_cs_2_0/task-template/tests/evaluate.py
• Measured selected DuckDB SQLLogicTest smoke files in the judge image: 5 files, 114 SQLLogicTest blocks, 438 assertions, ~0.3-0.4s.
• Harbor trial: frontier-cs-2-0-duckdb-e2e-query__xHLegDz
  • Async submissions used quick feedback: scale_factor_count=1, benchmark_count=22, ~52-55s each.
  • Final verifier used full scoring: submission_role=final, scale_factor_count=3, correctness_case_count=66, benchmark_count=66.
  • Final SQLLogicTest gate ran: final_sqllogictest=1, final_sqllogictest_count=5, final_sqllogictest_seconds=0.323.
  • Hidden query/scale/per-query/stderr leakage grep found no matches in verifier/agent submission logs.

Checklist

• Code follows the project structure and conventions
• Self-review completed
• Documentation updated (if applicable)

CI Validation (for new problems)

When adding new problems, CI will automatically validate that your reference solution achieves score > 0.

• Algorithmic problems: Include reference.cpp in your problem directory
• Research problems: Include reference.py (or reference.cpp if language: cpp in config.yaml)
• 2.0 problems: Include reference.py unless the problem config declares another language