P2 shipped the wrong rule and the title is the counter-example. I had reasoned
that the exit is the final untimed keyframe, so anything timed was still the
entry. It is not: `pteff02` on the title holds at t=46 with the 25 % dim quad at
alpha 0x40 and then ramps to 0x00 by t=236. The exit can be a long run of TIMED
keyframes, and running to the end drops the dim and leaves the whole screen
~13/255 too bright -- exactly the luminance excess P2 recorded (oracle 64.1,
rest 62.8, timeline 80.0) and filed as an unexplained "glow slab".
A group is pre-roll -> ramp in -> hold -> ramp out -> post-roll, and a screen
that has arrived sits on the hold. `settle_units()` is now `rest.t`, the
decoders' own identification of that hold.
The check is that a disagreement vanishes: on ALL TWELVE screens the settled
timeline is now byte-identical to the `--pose=rest` render, where before this
four differed by up to 247/255. The timeline's endpoint should BE `rest` -- the
animation is what it adds, not a different destination -- so this is the
property to want, and it holds with no special case.
Credit where due: this came out of the RE agent measuring the title's dim quad
against a plate-free capture, in pursuit of a different question.
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