Implement ask session handoff flow

[mcollina]

Summary

• add first-class ask sessions for assistant↔human handoffs
• add a dedicated ask page with a simplified handoff flow and mobile-friendly continue controls
• wire githuman ask to create ask sessions, wait for completion, and print collected feedback
• tighten ask feedback scoping and add route/web/cli coverage

Testing

• npm run typecheck
• npm test
• npm run lint
• npm run build