Extend scanline sweep to cover the full glitch window

SCANLINE_SWEEP_DURATION was still a flat 160 ticks (8s) from when
GLITCH_ACTIVE_SECONDS only covered a short burst -- fine at the time,
since nothing animated past that burst anyway. Once GLITCH_ACTIVE_SECONDS
was extended to cover the full show_static window, this fell behind:
animation.Transformation holds at its last keyframe once its own
declared duration elapses, so the scanline sweep visibly froze partway
through while jitter/bands (sized against the full window) kept
animating -- reported as "scanlines stop, but everything else is
running."

SCANLINE_SWEEP_DURATION is now derived from GLITCH_ACTIVE_SECONDS, same
as jitter already is. _SCANLINE_CYCLE_TICKS (sweep speed) is kept fixed
and SCANLINE_CYCLES derived from it, rather than the reverse, so the
sweep doesn't also slow down as the window gets longer.

Verified 1 negligible black-corner hit across 250 frames (consistent
with the known benign corner-tick color blend, not a structural issue),
327KB worst-case payload (strong zoom + random position), well under
the 460KB limit.

subwave_nowplaying.star

@@ -596,9 +596,21 @@ def _glitch_jitter(zoom):
 # small periodic shifts are the only mechanism that actually works here.
 SCANLINE_COUNT = 4
 SCANLINE_SPACING = ART_SLOT // SCANLINE_COUNT
-SCANLINE_SWEEP_DURATION = 160  # 8s total at the default 50ms/tick
-SCANLINE_CYCLES = 8  # how many times the sawtooth below repeats over that
-_SCANLINE_CYCLE_TICKS = SCANLINE_SWEEP_DURATION // SCANLINE_CYCLES
+
+# Sized against the full show_static window (GLITCH_ACTIVE_SECONDS), not
+# a fixed 8s -- it used to be a flat 160 ticks while GLITCH_ACTIVE_SECONDS
+# only covered a short burst, which was fine since nothing animated past
+# that burst anyway. Once GLITCH_ACTIVE_SECONDS was extended to cover the
+# full window, this fell behind: animation.Transformation holds at its
+# last keyframe once its own declared duration is up, so the scanline
+# sweep visibly froze (while jitter/bands, sized against the full window,
+# kept animating) for however much of the window was left after 8s.
+# _SCANLINE_CYCLE_TICKS is kept fixed (same sweep speed as before) and
+# SCANLINE_CYCLES derived from it, rather than the other way around, so
+# extending the window doesn't also slow the sweep down.
+_SCANLINE_CYCLE_TICKS = 20  # 1s per sawtooth cycle at the default 50ms/tick
+SCANLINE_SWEEP_DURATION = GLITCH_ACTIVE_SECONDS * _GLITCH_TICKS_PER_SECOND
+SCANLINE_CYCLES = SCANLINE_SWEEP_DURATION // _SCANLINE_CYCLE_TICKS
 
 def _glitch_scanlines():
     # Modeled on SUB/WAVE's own scanlines, which sweep continuously via