0a026074d3
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.