[bandzalkin]

Summary

This delivers OMP's structured ask questions to the Band room without blocking the room's serial message queue. Waiting for a participant inside the current turn prevents their answer from being processed; cancelling the native dialog aborts the prompt instead.

• Enable set_ask_dialog for each native session and fail startup if OMP cannot enable it.
• Post the questions, options, descriptions and recommendations through Band's canonical reply delivery path, mentioning the requester. Successful delivery counts as this turn's reply.
• Acknowledge delivery to OMP without selecting options or inventing a participant answer. The current turn can finish, and the participant's later message resumes the same native session.
• Preserve delivery failures and missing-reply reporting. A stop for the active room ends its turn; a stop for another room is treated as a failed post, not authority to stop this room.
• Refuse new UI and host-tool callbacks once native shutdown begins, so they cannot post after their owner starts closing.

Depends on #763. This handles the active room's structured ask dialog, not subagent UI forwarding.

Validation

Regression coverage checks rendered questions and recommendations, successful reply accounting, second-turn session reuse, failed posts, room-scoped stops, cancellation and callbacks arriving during shutdown. Native wire coverage checks the structured dialog schema.

[bandzalkin]

Closing: superseded by in-repo PR(s) #900 with the same content, one concern each and a clean single-author history.