## Why
Queued prompts and `request_user_input` answers can be persisted in a different
order from when the host accepted them. Using persistence order can therefore
reorder retained instructions during replay or apply the wrong rollback
boundary.
## What changed
- Reserve an acceptance sequence for user prompts and elicitation responses
when retained thread context is enabled.
- Persist that sequence with user-message metadata and verified answers, and
use it when ordering, bounding, replaying, and rolling back retained context.
- Keep events without acceptance metadata compatible with legacy recording
order.
## Testing
- Cover delayed queued-input recording, rejected prompts, checkpoint replay,
compaction, rollback migration, and legacy retained-context behavior.
GitOrigin-RevId: 42d24465cc2033bc51c0c2da79d3c0884a8ad98a