memory: U7 re-measured before scoping — pre-work only, no unit started

The standing instruction is to re-count the booths before scoping U7. Done
against the live 19-booth set, so the scope call is a short read rather than an
investigation.

Two findings. Sections are worth zero and it is now measured twice: not one of
the eleven gallery booths has a subdirectory, and the only two booths that do
are both reports, the job where grid navigation matters least. And the grouping
signal is in the filename rather than the tree -- stripping a trailing digit-run
yields 5 to 16 sensible groups on four of the five large galleries and
degenerates to one group on the fifth, while the competing split-on-second-
hyphen heuristic is useless everywhere.

The sizing case has also moved: the unit was scoped against 270-item booths and
the largest gallery is now 81 items / 40 images.

No U7 code and no U7 contract. The scope direction is the operator's call.

persistent-memory.md

@@ -78,6 +78,7 @@ _As of 2026-09-22:_
 
 ## Recent decisions
 
+- `[2026-09-22]` **U7 re-measured before scoping — sections are dead, filename prefixes are not** — PRE-WORK ONLY, no unit started; read before writing U7's contract → `persistent-memory.d/2026-09-22-u7-remeasured-before-scoping.md`
 - `[2026-09-22]` **The last open defect closed, and building its falsifier found another** — the wrong-shaped answer fixed at `_hydrate`; `_safe_fragments` lost its natural trigger and its handler could not survive the failure it handled → `persistent-memory.d/2026-09-22-a-wrong-shaped-answer-500s-the-gallery.md`
 - `[2026-09-22]` **U6 released as `v0.6.0` — benches, and the number that was two defects** — six of seven v1 units landed, NOT PUSHED → `persistent-memory.d/2026-09-22-u6-benches-released.md`
 - `[2026-09-22]` **Three cold panels on one unit, and what each lens could only see alone** — READ BEFORE DECIDING TO SKIP A GATE; all five passes found something the others structurally could not → `persistent-memory.d/2026-09-22-three-cold-panels-on-one-unit.md`