agent: the loop must never stop itself

A run ended with a clean exit 0 while the display title read "Loop interval
optimization", leaving four files uncommitted in the tree. Nothing crashed --
the loop was ended, and ending the loop ends the run: the container exits and
there is no next iteration.

The prompt said the agent did not NEED to arm a wakeup. It never said not to
stop one, and an agent that reads about a pacing control will reasonably try to
use it. Now explicit: do not call ScheduleWakeup at all, and if the cadence is
wrong, say so and leave it to a human -- the interval is set outside the prompt.

Recorded with the date and the symptom, because "the container exited cleanly"
looks like a finished job rather than a self-inflicted stop.

docker/agent/loop-task.md

@@ -120,3 +120,13 @@ turn ends — but sequential tool calls within a turn are fine.
 
 The loop runs on a fixed interval set by the harness, so you do **not** need to
 arm the next wakeup yourself. Spend that attention on the write-up instead.
+
+**And never stop it.** Do not call `ScheduleWakeup` at all — not to re-pace the
+loop, not to tidy up, and above all not with `stop`. Ending the loop ends the
+run: the container exits, and the next iteration never happens. If the cadence
+is genuinely wrong, say so in your reply and leave it to a human — the interval
+is set outside this prompt and is not yours to optimise.
+
+This is not hypothetical. A run ended at 2026-08-29 04:0x with a clean exit 0
+while the display title read "Loop interval optimization", leaving four files of
+work uncommitted in the tree.