[codex] Add evidence conflict alerts

[judefluen-coder]

Summary

• Detect evidence level conflicts when a company mapping is labeled stronger than its strongest underlying evidence source.
• Surface conflict alerts through mapping quality alerts, company detail alerts, and coverage overview insights.
• Update README and smoke coverage so conflict detection remains part of the product contract.

Validation

• npm run smoke
• npm run validate:example
• npm run validate:tabular
• npm run build
• git diff --check