memory: no fleetwide notice for U4, and the measurement caveat it creates

Operator decision 2026-09-22: no broadcast to the 17 consuming handles. Same
posture as U5 — adoption gets told apart from design because nobody was primed.

The consequence is a measurement one and it needed writing down before it was
lost. U4's two halves have different adoption costs: the hold rides for free
(a session runs `booth ask` and its booth is held, knowing nothing), but NOT
pressing `keep` has to be learned. So a flat `.forever` rate on 2026-10-06 is
exactly what 'the mechanism works and nobody was told' looks like, and reading
it as a falsification would retire a correct diagnosis on an uncontrolled
measurement.

Records the three counts to report instead, and states the sensitivity floor:
only 4 of 24 booths carry marks at all, so the hold can touch at most a sixth
of the fleet and an effect below one or two booths is not resolvable.

persistent-memory.d/2026-09-22-no-notice-and-what-it-does-to-the-prediction.md

@@ -0,0 +1,54 @@
+# No fleetwide notice for U4 — and what that does to the prediction
+
+_2026-09-22 · booth_
+
+**Operator decision, 2026-09-22: do NOT tell the 17 consuming handles that
+`keep` has stopped being the way to say "waiting on an answer".** No broadcast.
+Same posture he took on U5, and the same instrument: adoption gets told apart
+from design because nobody was primed.
+
+⚠ **THIS CHANGES HOW THE 2026-10-06 RE-COUNT MUST BE READ, and a session that
+misses this will draw the wrong conclusion from a true number.**
+
+U4 has two halves and they do NOT have the same adoption cost:
+
+- **The hold rides for free.** A session that runs `booth ask` gets its booth
+  held with no knowledge of anything. The operator answering releases it. No
+  peer has to learn a thing for the mechanism to work.
+- **NOT PRESSING `keep` HAS TO BE LEARNED.** U4 makes the sentinel unnecessary
+  for the "not yet" case; it does not make it unavailable, and nothing stops a
+  habit. An agent that has always pressed `keep` while waiting will keep
+  pressing it.
+
+**So a flat `.forever` rate on 2026-10-06 does NOT falsify the diagnosis.** It
+is exactly what "the mechanism works and nobody was told" looks like — the U5
+shape, one unit later. Reporting a null result without this caveat would retire
+a correct diagnosis on the strength of an uncontrolled measurement.
+
+**Use these instead, and report all three.** The raw rate stays as context, not
+as the verdict:
+
+1. **The overlap — booths with an open pick AND `.forever`.** Was **3** on
+   2026-09-22, which is the positive control for the whole diagnosis. It falls
+   only if peers learn; it is the *adoption* number.
+
+       comm -12 <(grep -l '"shape": "pick"' ~/booth-data/*/.marks.json | xargs -n1 dirname | sort) \
+                <(dirname ~/booth-data/*/.forever | sort) | wc -l
+
+2. **Did the hold ever bind?** Count booths that were held past their TTL and
+   therefore survived a sweep they would otherwise have lost. This needs no
+   peer to change anything, so it is the honest test of whether the mechanism
+   is load-bearing at all. **If it is ZERO over a fortnight, the diagnosis was
+   wrong about VOLUME** — the "not yet" case is rarer than the sentinel rate
+   suggested — and that is a real finding. The sweeper logs what it wipes;
+   nothing yet logs what it spares, so **this counter does not exist and would
+   have to be added before it can be read.** Say so rather than guessing.
+3. **The raw `.forever` rate** — 17 of 24 (70%) on 2026-09-22. Context only,
+   now that the no-notice decision has made it a measurement of habit rather
+   than of need.
+
+⚠ **Sensitivity floor, stated because a bare "no effect" is unfalsifiable:**
+only **4 of 24** booths carried marks at all on 2026-09-22. The hold cannot
+bind on a booth with no marks, so at that population the mechanism can touch at
+most a sixth of the fleet, and an effect smaller than one or two booths is not
+resolvable by any of these counts. Related: `[[2026-09-22-forever-had-a-live-positive-control]]`.