Fix Strategy 27 closed snapshot validation

[jackhai9]

Summary

• allow a closed event to retain the last eligible snapshot before its lifecycle boundary
• keep the event-closed timestamp bound to active_end_at_ms
• publish the generated Strategy 27 userscript as version 0.1.2

Validation

• npm run test:binance-strategy27-events
• npm test
• npm run build:binance-strategy27-events
• npm run check:binance-userscripts
• npm run inspect:binance-strategy27-events
• git diff --check