docs: backlog — primitive layers tabled; the tie-break is now the only gap

docs/re/BACKLOG.md

@@ -107,22 +107,27 @@ See [`structures/ui-composable-bundles.md`](structures/ui-composable-bundles.md)
   title — the one screen with ground truth — it takes mean luminance from **+18 %
   to −1.3 %** of the capture (76.30 → 63.72 vs 64.58) and mean abs diff 16.07 →
   13.08. Off by default because of the item below.
-* 🟡 **Where a primitive paints — three measured screens, still no derivation**
-  (2026-08-19). A primitive has no `T8aD` header and so no layer key. Measured
-  positions are stable **by role**: `palogo_eff0.prm` (opaque backdrop) **first**
-  on the splash; `pteff02.prm` (25 % dim) at slot **4** on both the title and the
-  main menu; `pteff00.prm` (transition fade) **last** on both. Nothing in the
-  file predicts this — any key must live in the 60-byte declaration entry, of
-  which four words are still unread. **That is the next first step**, and it is
-  a *static* task now: dump the full declaration entries for these three screens
-  and look for a word that sorts like the measured orders.
-  ✅ Input was never the blocker — the game receives the Ⓐ press
-  (`vk=5800 flags=0001`, measured); four harness bugs were. Boots now reach the
-  main menu, whose composite scores **0.9591** against a live capture.
-  ❔ `GP_DIALOG` DIFFICULTY remains unreached: Ⓐ on NEW GAME hits the standing
-  black-screen hang.
-  See [`structures/ui-paint-order-key.md`](structures/ui-paint-order-key.md) and
-  [`ui-paint-order-third-permutation.md`](ui-paint-order-third-permutation.md).
+* 🟡 **Where a primitive paints — not in the file; measured and tabled**
+  (2026-08-19). 🔴 Refuted twice over: the declaration entry's four unread words
+  are **constant** (`+28`=0, `+36`=0xffffffff, `+56`=0, `+44` a button ordinal),
+  and the bundle carries **no data at all** for a primitive — the menu build
+  declares three and has zero RATC children for any of them. The layer comes
+  from the game's code. ✅ But it is consistent: `pteff02.prm` implies a key in
+  **(0x8010, 0x8040) on both** screens it appears on, `pteff00.prm` past the
+  maximum on both, `palogo_eff0.prm` below the minimum. `implied_layer_key`
+  records those, and `derived_paint_order` now reproduces the **layer-key
+  sequence of all three measured orders**, primitives included (element-for-
+  element on 4 of 5 bundle instances; the title differs only inside tied groups).
+  ❔ **Still open:** primitives whose position has never been measured —
+  `pzeff00.prm` and `pceff00.prm` are what wipe the 36 builds, which is why
+  `include_primitives` stays off by default. A capture of any screen carrying one
+  would close it.
+  See [`structures/ui-prm-primitives.md`](structures/ui-prm-primitives.md).
+* ❔ **The tie-break.** Elements sharing a layer key are painted in an order
+  nothing predicts — the title's `0x8083` ×5 group paints `14,15,18,16,17` and
+  the `0x80a0` ×7 group paints `0,2,4,7,1,3,5`. Now the *only* thing between the
+  derived order and the measured ones, so it is the next cheap static probe:
+  three measured screens' tied groups against every remaining field.
 * ❔ **Blend mode.** Everything is straight alpha-over. The near-white flash
   quads (`0xf0ffffff`) and coloured ones (`0x60ff0000`) may be additive. The
   title capture cannot separate the two — its resting elements are all