port: the (A) snap RESTARTS the leaves at t=0, not just the shared clock

Measured by the Decoder with the full-quad reader: at the snap frame both sweeps
enter at their DECLARED OPENING alphas -- pteff03 at 255, pteff03a at 0 rising
1,2,3,4,6,11,17 from x=1721. Those are the leaves' own t=0 poses.

My implementation advanced the shared clock and left the leaf phase untouched, so
the sweeps would have sat mid-travel at the right clock value and the wrong
position. A defect visible only in a film -- no still and no clock reading would
show it, because the clock was correct.

The field already existed (leaf_start_units, from the F6 work); it simply was not
being set at the snap.

VERIFIED, pre-registered, via --probe-leaf on a real boot with a real press:
  snap frame  -> leaf_t 0.0, pteff03 x=-639, pteff03a x=1721  (declared t=0)
  next frame  -> leaf_t 0.5, both advanced by 2 px

Their separate note on my snap target: 236.0 survives their challenge -- at the
snap the sweeps are at alpha 255, putting the title clock in [100,238) -- but
their data cannot separate 236 from 200. Recorded as surviving, not confirmed;
the bound in the code comment already says so.

port/scripts/boot.gd

@@ -995,8 +995,20 @@ func _unhandled_input(event: InputEvent) -> void:
 	if overlay != null and event.is_action_pressed("ui_accept"):
 		var snap_to := overlay.settle_time()
 		if snap_to > 0.0 and view.time_units < snap_to:
-			print("  (A) snaps the title: shared clock %.1f -> %.1f" % [view.time_units, snap_to])
+			print("  (A) snaps the title: shared clock %.1f -> %.1f, leaves restart at 0"
+				% [view.time_units, snap_to])
 			view.time_units = snap_to
+			# 🔴 THE LEAVES RESTART AT THEIR OWN t=0; the snap is not only a clock
+			# advance. MEASURED: at the snap frame both sweeps enter at their
+			# DECLARED OPENING alphas -- `pteff03` at 255, `pteff03a` at 0 rising
+			# 1,2,3,4,6,11,17 from x=1721
+			# (`docs/re/f5-verified-with-full-quad-reader.md`).
+			#
+			# Advancing the shared clock alone would leave the leaf phase where it
+			# was, so the sweeps would sit mid-travel at the right clock value and
+			# the wrong position -- a defect visible only in a film, and one this
+			# implementation had until this line.
+			view.leaf_start_units = snap_to
 			view.queue_redraw()
 			_overlay_process(0.0)
 			return