Disable RGB-split bands, re-enable scanlines, fix base jitter cancelling out

Commented out the two _glitch_band calls per request (RGB-split bands
off), re-enabled _glitch_scanlines.

Also found and fixed a real bug in the base jitter: base_shift was
derived by averaging each state's shift1/shift2 values, but several
GLITCH_STATE_POOL entries have those nearly or exactly cancel out (e.g.
-2 and 2 average to 0), silently zeroing out the jitter in about half
the burst states -- likely why it wasn't visible. Now alternates a fixed
+1/-1 by position in the sequence instead, so it's never zero.

subwave_nowplaying.star

@@ -478,18 +478,23 @@ def _glitch_jitter(zoom):
     pause = _glitch_hold(render.Box(width = ART_SLOT, height = ART_SLOT), GLITCH_PAUSE_TICKS)
 
     sequence = []
+    state_index = 0
     for cycle_index in range(GLITCH_REPEATS):
         for top1, h1, shift1, hue1, top2, h2, shift2, hue2 in _glitch_states_for_cycle(cycle_index):
             # The art itself nudges along with the bands, not just the
-            # bands moving over a static image. Capped to +-1px (rather
-            # than splitting the difference between the two bands' own,
-            # larger shift values) -- a full-frame shift reads very
-            # differently than a thin band shifting, so it stays subtle.
-            base_shift = max(-1, min(1, int((shift1 + shift2) / 2.0)))
+            # bands moving over a static image. Capped to +-1px -- a
+            # full-frame shift reads very differently than a thin band
+            # shifting, so it stays subtle. Alternates +1/-1 by position
+            # in the sequence rather than deriving from shift1/shift2:
+            # several pool entries have those nearly or exactly
+            # cancel out (e.g. -2 and 2), which silently zeroed out the
+            # jitter in about half the states.
+            base_shift = 1 if state_index % 2 == 0 else -1
+            state_index += 1
             state = render.Stack(children = [
                 _glitch_base_jitter(zoom, base_shift),
-                _glitch_band(zoom, top1, h1, shift1, hue1),
-                _glitch_band(zoom, top2, h2, shift2, hue2),
+                # _glitch_band(zoom, top1, h1, shift1, hue1),
+                # _glitch_band(zoom, top2, h2, shift2, hue2),
             ])
             sequence.append(_glitch_hold(state, GLITCH_HOLD_TICKS))
         sequence.append(pause)
@@ -560,7 +565,7 @@ def _glitch_effect(zoom):
         height = ART_SLOT,
         child = render.Stack(children = [
             _glitch_jitter(zoom),
-            # _glitch_scanlines(),  # disabled -- was making the jitter hard to see
+            _glitch_scanlines(),
             _glitch_corner_ticks("#00000080"),
         ]),
     )