P3. The exit is the group playing ITSELF out, not a black rect over a frozen
screen -- and that was settled by a test that discriminates rather than by
plausibility. Under the black-rect model every region is scaled by the same
1-alpha, so the button/background brightness RATIO would hold constant through
the fade; measured, it falls 6.495 -> 5.574 -> 3.105 -> 2.125 -> 1.935.
Implemented by giving the final untimed keyframe a SYNTHETIC time,
exit_ramp_units after the last timed one, then interpolating it like any other
frame. One code path: arriving and leaving differ only in how far `t` is allowed
to run, not in kind. `holding` is what the sequencer clears to send a screen away.
The sequencer waits on nothing the disc does not carry. A screen holds until its
own group has arrived, then plays out; `dwell` in flow.json is deliberately empty
because each screen's dwell IS its keyframe group (publisher wordmark 3.92 s,
developer logos 3.17 s, both read from the disc). Any extra hold would be a
number nobody measured.
The last screen keeps holding -- nothing is taking the title's place, and a boot
that ends by fading to black looks like a boot that crashed.
flow.json reproduces an OBSERVATION and says so in its header: Q6 closed with a
negative, the order is on the disc nowhere, a transition is a call with a name
argument chosen by code. The intro video's place in the real boot is named as a
gap rather than the order being quietly rewritten to hide it.
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