re: REGN cell payload indexes neither points nor planes -- static search exhausted

The previous test only tried section-1 targets. Closing that gap: the payload's
three index-shaped u32s, followed into the point list and the plane list and
checked for the target lying inside the referencing cell, all sit at the 0.203%
random control.

Two cells read 0.81%, 4x the baseline. I am not treating that as a lead: across
this and the previous iteration roughly twenty such tests have been run, and at
that count a single 4x enrichment on ~8000 trials is what noise looks like.
Calling it a signal would be the multiple-comparisons error a long hypothesis
sweep invites.

So REGN's header, grid, points, planes and cell index are decoded, section 1's
slot regions are censused, and the link between the grid and the geometry is not
reachable by any static test I can construct. The honest next step is the PE
code that reads a REGN object -- the same kind of work that cracked the .slb
packing phase -- rather than a twenty-first correlation.

docs/re/BACKLOG.md

@@ -354,7 +354,11 @@ search cannot find a *schedule*.
   and section 2's exactly 96, in 11/11). **Section 0 is a point list**
   (13 467/13 467 inside the bbox) and **section 2 is a plane list** — unit normal,
   signed distance, and a point, with `n·p + d = 0` to float round-off in
-  **133 573/133 573**. Section 1 (96 B) still ❔.
+  **133 573/133 573**. Section 1 (96 B) still ❔ in meaning, though its slot
+  regions are censused. ❌ **The static coupling search is exhausted**: every
+  index-shaped field in the cell payload has been followed into all three
+  sections and checked for spatial agreement against controls — nothing above
+  chance. Settling it needs the PE code that reads `REGN`, not more correlation.
   See [`structures/regn-map-grid.md`](structures/regn-map-grid.md).
 * 🔴 **`hidden/DefTables.pak` is NOT it** (checked 2026-08-24). The three
   unnamed schemas are more **model/render** tables in the same vocabulary as the