A task that reports a roadblock but finishes successfully (Done/WaitingForReview/
Failed/Cancelled) had no way to answer it short of a full reset-and-rerun, losing
the run's context. Adds a reply textbox + Send button to the existing ROADBLOCK
card, modeled on the AskUser question card, that resumes the session via
ContinueTaskAsync with the user's own text. Gated on LatestRunSessionId (disabled
with a hint when there's nothing to resume); failures surface through the footer
error strip instead of a modal.
