leo: add decision_market entity type + Key Decisions table format
- New entity_type: decision_market for governance proposals, prediction
markets, and futarchy decisions
- Terminal lifecycle: active | passed | failed
- Platform-specific volume fields (futarchy, ICO, prediction market)
- Categories: treasury, fundraise, hiring, mechanism, liquidation, grants, strategy
- Parent entities get Key Decisions summary table (date, title, proposer, volume, outcome)
- Significance threshold: ~33-40% of real proposals qualify
- 5-point mechanical eval checklist
- Reviewed by Rio (domain data structure) and Ganymede (architecture)
Pentagon-Agent: Leo <14FF9C29-CABF-40C8-8808-B0B495D03FF8>