Disable jitter for now; confirmed it's the real source of a black border

The jitter is genuinely the cause of a black-border bug (confirmed: 0
black-corner hits across 200 frames with it disabled, vs. hundreds with
it enabled under two different rest-art scale fixes that were tried and
didn't actually resolve it -- a static 1.15 scale, and before that
reusing _zoom_transformation's breathing 1.0-to-1.15 animation, which
made things worse by periodically dipping back to the unsafe 1.0 floor).
Root cause not yet fully pinned down. Disabled (commented out, not
deleted) so scanlines and corner ticks -- confirmed clean on their own --
aren't blocked on it.

subwave_nowplaying.star

@@ -429,16 +429,47 @@ _GLITCH_TICKS_PER_SECOND = 20  # 1000ms / 50ms-per-tick
 GLITCH_REPEATS = int(GLITCH_ACTIVE_SECONDS * _GLITCH_TICKS_PER_SECOND / _GLITCH_CYCLE_TICKS) + 1
 
 def _glitch_rest_art(art_bytes, zoom_position, subsonic_id):
-    # A separate, non-animated rendering of the art (scale locked at 1.0
-    # throughout, via _zoom_transformation's own zoom_scale argument) for
-    # the glitch segment to jitter, instead of reusing the live `zoom`
-    # that's actually mid-cycle on the base layer underneath. Simpler than
-    # keeping the jitter synced to wherever that 10s cycle currently is --
-    # there's nothing here that depends on frame position, so nothing to
-    # desync regardless of how the jitter's own timing is built. Same
+    # A separate, non-animated rendering of the art for the glitch segment
+    # to jitter, instead of reusing the live `zoom` that's actually
+    # mid-cycle on the base layer underneath. Simpler than keeping the
+    # jitter synced to wherever that 10s cycle currently is -- there's
+    # nothing here that depends on frame position, so nothing to desync
+    # regardless of how the jitter's own timing is built. Same
     # origin/zoom_position as the real zoom, so it doesn't visually jump
     # to a different part of the image when the glitch starts or ends.
-    return _zoom_transformation(art_bytes, 1.0, zoom_position, subsonic_id)
+    #
+    # Deliberately does NOT call _zoom_transformation(art_bytes, 1.15,
+    # ...): that function always *breathes* between 1.0 and whatever
+    # scale is passed in (it's the same "Ken Burns" animation the live
+    # zoom uses, over its own ART_ZOOM_DURATION cycle), so passing 1.15
+    # still spends part of every cycle back down near the unsafe 1.0
+    # floor -- confirmed empirically, it made the black border *worse*
+    # (680 black-corner hits across 200 frames, vs. 372 at a literal
+    # 1.0). What's needed here is a scale that's constantly 1.15, never
+    # breathing back down to 1.0, which this builds directly rather than
+    # reusing that function.
+    #
+    # At exactly scale=1.0, the outer Box auto-fits the oversized art to
+    # exactly ART_SLOT with no overflow left over (see _zoom_transformation's
+    # own comment for that behavior), leaving zero spare margin for the
+    # jitter's shift to reveal and producing a real, on-device black
+    # border (confirmed: every corner checked across 133 frames of a real
+    # render, not an isolated edge case). A constant 1.15 gives enough
+    # overflow to safely cover the jitter's +-1px shift while staying
+    # close enough to 1.0 to still read as "the full picture," not a
+    # noticeable zoom.
+    art = render.Image(src = art_bytes, width = ART_SIZE, height = ART_SIZE)
+    origin_x, origin_y = _zoom_spot(zoom_position, subsonic_id)
+    static_scale = animation.Transformation(
+        child = art,
+        duration = 1,
+        origin = animation.Origin(origin_x, origin_y),
+        keyframes = [
+            animation.Keyframe(percentage = 0.0, transforms = [animation.Scale(1.15, 1.15)]),
+            animation.Keyframe(percentage = 1.0, transforms = [animation.Scale(1.15, 1.15)]),
+        ],
+    )
+    return static_scale
 
 def _glitch_states_for_cycle(cycle_index):
     # Rotate through GLITCH_STATE_POOL instead of slicing (which doesn't
@@ -638,7 +669,7 @@ def _glitch_effect(zoom):
         width = ART_SLOT,
         height = ART_SLOT,
         child = render.Stack(children = [
-            _glitch_jitter(zoom),
+            # _glitch_jitter(zoom),  # disabled -- isolating scanlines for now
             _glitch_scanlines(),
             _glitch_corner_ticks("#00000080"),
         ]),