Add structured feedback for investigation open questions

[Neokil]

Summary

• parse strict Open Questions lists from the current actionable artifact
• render one textarea per open question plus additional feedback
• submit structured markdown feedback while keeping the existing backend API contract
• add parser, panel, and app-level tests for the new flow

Testing

• cd web && npm test
• cd web && npm run lint
• cd web && npm run typecheck
• cd web && npm run build
• go test ./...

Notes

• golangci-lint run still reports existing repository issues in generated code and sibling .auto-pr/worktrees, which are unrelated to this ticket.

[Neokil]

This change fails the e2e tests and also it causes an infinite reload loop