Answers the Decoder's direct question: the port positions the leaf from the
LEAF's own clock, it does not draw the parent's pose and ignore the translation.
Computed from the leaf translation: pteff03 enters the frame at t=61 and is
mid-screen (x=305) when the plate reaches full alpha at t=236 -- visible and
travelling for ~175 units before the plate.
And screen_view.gd's own flagged limit -- 'a capture during t=100..238 would
separate' leaf-wins from parent-ignored-because-it-draws-nothing -- is the SAME
interval F6 is about. Applying the parent would hide the sweep until t=70 and
dim it to t=100, which accounts for ~40 units of the earliness but not the other
~175. One capture in that window settles both questions.
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