Fix OpenAI strict verdict extraction schema

[ernestprovo23]

Summary

• require every declared property in the verdict extraction schema for OpenAI strict structured output
• remove engine-computed nested consensus and optional vote confidence from the extraction contract
• version the extraction prompt and require honest empty values for semantic optionals
• validate frozen replay verdict payloads recursively against the extraction schema

Verification

• 716 tests passed
• Ruff check and format check passed
• git diff check passed
• Gitleaks found no leaks
• read-only adversarial review clean

Live evidence

The capped paid smoke reached all providers but OpenAI rejected the previous strict schema before generation because declared properties were missing from required. This PR fixes that exact provider error; a fresh capped live matrix follows after merge.