docs: one page saying how good the five screens actually are

The answers for the port's five screens were spread across a dozen
documents and none of them said how good the result IS. Measured:

  screen              build  drawn   corr vs capture  alignment
  title                 4    15/24      +0.9500       dy=0 dx=0
  main menu             5    11/16      +0.9460       dy=0 dx=0
  EXTRAS                6    13/18      +0.9440       dy=0 dx=0
  publisher splash     10     2/3       +0.9600       dy=0 dx=0
  developer splash     11     6/7       +0.9643       dy=0 dx=0

Every one aligns at exactly zero offset over a +/-2 px search in both
axes, so placement and scale are right and the residual is tone and
detail rather than geometry.

The drawn/total counts are not slack. Each undrawn element has a reason
already documented: kind & 0x4 ghost instances (4 on the title), .prm
primitives off by default (2 per menu, 1 per splash), loop* animations
off by default and off-screen at rest (2 per menu screen), and the 8AX
name mismatch (1 per menu screen) whose art reaches the screen anyway via
ptbase. 4+2+2+1 = 9, 2+2+1 = 5, 1. Nothing unexplained.

The residual is ranked for a consumer: tone first (gamma 1.34-1.49, the
game's own display ramp), then 8AX resolution, then one drawable
paint-order tie on EXTRAS alone, then rotation-decoded-but-not-rendered
which does not affect these five at rest.

Reach stated: these are static composites at the resting pose against
single frames, so nothing here speaks to animation, and a whole-frame
correlation is a sanity figure rather than a per-element check.

docs/re/five-screens-acceptance.md

@@ -0,0 +1,63 @@
+# ✅ The five screens, end to end — what each one is actually worth
+
+**Status:** ✅ measured, 2026-08-29. One page, because the answers for these five
+screens are otherwise spread across a dozen documents and none of them says how
+good the result *is*.
+
+Rendered with `sylpheed-cli screen render` (adding `--all --black` for the two
+splash halves) and correlated against the committed live captures.
+
+| screen | build | elements drawn | corr vs capture | alignment |
+|---|---|---|---|---|
+| title | 4 | 15 / 24 | **+0.9500** | dy=0 dx=0 |
+| main menu | 5 | 11 / 16 | **+0.9460** | dy=0 dx=0 |
+| `EXTRAS` | 6 | 13 / 18 | **+0.9440** | dy=0 dx=0 |
+| publisher splash | 10 | 2 / 3 | **+0.9600** | dy=0 dx=0 |
+| developer splash | 11 | 6 / 7 | **+0.9643** | dy=0 dx=0 |
+
+Every one aligns at **exactly zero offset** — searched ±2 px in both axes — so
+placement and scale are right and the residual is tone and detail, not geometry.
+
+## Every omission is accounted for
+
+The counts are not slack; each undrawn element has a reason already documented:
+
+| screen | not drawn | why |
+|---|---|---|
+| title | `ptlogo1`×2, `ptlogo2`×2 | `kind & 0x4` **ghost instances** — the draw capture shows one quad per wordmark |
+| | `pteff00.prm`, `pteff02.prm` | `.prm` primitives, off without `--primitives` |
+| | `ptloop01.rat`, `ptloop02.rat` | `loop*` animations, off without `--animated`; at rest both sit off-screen |
+| | `pteff04.t32` | the **`8AX` name mismatch** — the art *is* on screen, drawn via `ptbase2` ([8AX](structures/ui-8ax-fullres-background.md)) |
+| main menu, `EXTRAS` | 2 `.prm` + 2 `loop*` + `pteff05.t32` | same three reasons |
+| both splashes | `palogo_eff0.prm` | `.prm` primitive |
+
+4 + 2 + 2 + 1 = 9 on the title; 2 + 2 + 1 = 5 on each menu; 1 on each splash.
+**Nothing is unexplained.**
+
+## What the residual is, per screen
+
+Ranked by what a port would notice:
+
+1. **Tone.** The capture is darker than the composite by a gamma of ≈1.34–1.49
+   ([tone curve](structures/ui-render-tone-curve.md)) — the game's own display
+   ramp, not an emulator artefact. This is the largest single contributor to the
+   0.94–0.96 rather than higher.
+2. **`8AX` resolution.** The background is drawn from the 640×360 `ptbase`
+   upscaled 2×, where the game uses the native 1280×720 `8AX`
+   ([measured](structures/ui-8ax-fullres-background.md), two screens at 68 % of
+   ceiling).
+3. **Paint-order ties on `EXTRAS` only.** One drawable overlapping tie
+   (`ptframe3`×`ptframe4`), and the capture is consistent with our order
+   ([check](structures/ui-paint-order-derived-check.md)). The other four screens
+   use orders measured from the game.
+4. **Rotation is decoded but not rendered** — and does not affect any of these
+   five at rest ([rotation](structures/ui-keyframe-rotation.md)).
+
+## Reach
+
+* These are **static composites at the resting pose** against **single frames**.
+  Nothing here says the animation is right; Q1's interpolation law is settled but
+  a multi-keyframe group's absolute timing is not
+  ([time unit](ui-keyframe-time-unit.md)).
+* Correlation on a whole frame is dominated by large areas. It is a sanity figure,
+  not a per-element check — the per-element work is in the documents linked above.