Fix scanline loop-point flicker with an instantaneous snap-back

The ramp-end keyframe and the next cycle's snap-back-to-0 keyframe were
one tick apart, which got linearly interpolated -- for that one tick the
pattern sat at a fractional, not-quite-zero offset instead of cleanly
snapping, producing a brief flicker at each loop point. Fixed by giving
both keyframes the exact same percentage (a zero-duration jump) instead.

Also drops payload (425KB -> 364KB on the same test render) by removing
a redundant near-duplicate frame per cycle.

subwave_nowplaying.star

@@ -611,16 +611,22 @@ def _glitch_scanlines():
             lines.append(render.Box(width = ART_SLOT, height = 1, color = "#00000000"))
     pattern = render.Column(children = lines)
 
+    # The ramp's end and the next cycle's snap-back share the exact same
+    # percentage (a zero-duration jump), rather than the snap landing one
+    # tick later -- that one-tick gap got linearly interpolated, which
+    # for a single tick showed the pattern at a fractional, not-quite-0
+    # offset instead of cleanly snapping, producing a brief flicker right
+    # at the loop point.
     keyframes = []
     for cycle in range(SCANLINE_CYCLES):
         cycle_start = cycle * _SCANLINE_CYCLE_TICKS
-        ramp_end = cycle_start + _SCANLINE_CYCLE_TICKS - 1  # last tick of the cycle is the snap back to 0
+        cycle_end = cycle_start + _SCANLINE_CYCLE_TICKS  # == next cycle's cycle_start
         keyframes.append(animation.Keyframe(
             percentage = float(cycle_start) / SCANLINE_SWEEP_DURATION,
             transforms = [animation.Translate(0, 0)],
         ))
         keyframes.append(animation.Keyframe(
-            percentage = float(ramp_end) / SCANLINE_SWEEP_DURATION,
+            percentage = float(cycle_end) / SCANLINE_SWEEP_DURATION,
             transforms = [animation.Translate(0, SCANLINE_SPACING)],
             curve = "linear",
         ))