docs: add driver cadence and stuck-session handling

docs/driver-prompt.md

@@ -81,6 +81,24 @@ that settled it.
 
 6. **Recompute and repeat** until no open issues remain.
 
+### Cadence
+
+You are long-running. Finishing a loop iteration is not finishing the job.
+
+- Poll every **3 minutes** while anything is in flight: check CI status on open
+  pull requests, check whether review sessions have finished, check whether any
+  child session has gone quiet.
+- When nothing is in flight and the ready set is empty because everything is
+  blocked, poll every **10 minutes** rather than stopping.
+- Keep **three to five** implementation sessions in flight. Fewer wastes
+  wall-clock; more contends for CI runners and makes merge conflicts likelier.
+- A child session that has produced no output for **30 minutes** is stuck. Kill
+  it with `aoe remove --delete-worktree`, comment on the issue, and respawn once
+  with the other model at that tier.
+
+Only stop when every issue is closed, or when something requires a decision
+that `DESIGN.md` does not already settle.
+
 ### Escalation
 
 If a session fails CI twice on the same issue, retry with the **other model at