re(ui): a static composite is only meaningful for a screen that settles

The model's sharpest prediction, tested with its control. The draw log
says that on the developer splash the _eff glows are drawn on frames
94-115 and the logos on 116-211, so at the moment the reference capture
was taken EVERY glow is already finished -- including the two that have
plateaus and which rest_plateau therefore renders visible. Suppressing
them should help on the splashes and hurt where a screen genuinely
settles.

  publisher splash   +0.9604 -> +0.9982   +0.0377
  developer splash   +0.9659 -> +0.9980   +0.0321
  title    (control) +0.9500 -> +0.9480   -0.0020
  main menu(control) +0.9460 -> +0.8544   -0.0916
  EXTRAS   (control) +0.9440 -> +0.8370   -0.1070

Both splashes jump to about 0.998; all three persistent screens get
worse. The control is what makes this a finding rather than a
coincidence: the same edit helps exactly where the model says it should
and hurts exactly where it says it should not.

So rest_plateau is not over-drawing in general -- it over-draws on
TRANSIENT screens. A plateau mid-animation means the element is held at
that point in the timeline, not that it is on screen once the screen has
settled. Where a screen settles, the held pose IS the settled pose and
the rule is measurably right.

And that answers the question left open several iterations ago -- what
"rest" means for a transient element. It does not mean anything: the
splashes never rest. A static composite of them can match a chosen frame,
and about 0.998 is what these captures' frame is worth, but the format
does not answer a question the screen never poses.

For the port: play the timeline for the two splashes, which the settled
keyframe timing now supports, and composite statically for title, main
menu and EXTRAS.

METHOD: an edit that improves one set of cases is only interesting once
you have shown it damages the cases where it should.

docs/re/METHOD.md

@@ -787,3 +787,11 @@ agent's loop prompt, i.e. nowhere durable. See [`README.md`](README.md) for the
   completion* while the screen is still up. The exit is the dismissal, so a
   displayed screen never reaches its last keyframe. Both claims survive; what was
   wrong was the step between them that I supplied.
+* **The control is what turns a helpful edit into a finding.** Suppressing the
+  `_eff` glows raised both splashes from ≈0.96 to ≈0.998 — on its own that reads
+  as "we over-draw glows". Running the same edit on the three screens that settle
+  made them **worse** (−0.002, −0.092, −0.107), which is what makes the result
+  mean something specific: the over-draw is confined to transient screens, where
+  a plateau mid-animation is not evidence the element is on screen at rest. An
+  edit that improves one set of cases is only interesting once you have shown it
+  damages the cases where it should.