v0.55.0: Kaleidostrobe smooth again; visualizer tile hover controls

The cones move only on the plugin's own 25 fps frames again: driving them
from fresh audio every refresh made bass-heavy songs twitch (a jump on 84%
of refreshes against 41%). The continuous turn, texture crossfade and the
GPU big window stay.

The tile: a click opens it big (and it stays blank while big); hovering
shows a colour wheel (colour / gray / off) and up/down arrows (previous /
next visualizer). No more double-click or click-to-cycle. The big album
art closes on a click or Esc, like the big visualizer.

tests/test_round9.py

@@ -80,11 +80,11 @@ class TestVisualizerToggle:
         vis = VisualizerWidget(player)
 
         assert vis._mode == MODE_ON
-        vis.mousePressEvent(None)  # on -> dim
+        vis.cycle_mode()  # on -> dim
         assert vis._mode == MODE_DIM
-        vis.mousePressEvent(None)  # dim -> off
+        vis.cycle_mode()  # dim -> off
         assert vis._mode == MODE_OFF
-        vis.mousePressEvent(None)  # off -> on (wraps)
+        vis.cycle_mode()  # off -> on (wraps)
         assert vis._mode == MODE_ON
 
     def test_off_goes_blank_and_stops(self, qapp):
@@ -94,8 +94,8 @@ class TestVisualizerToggle:
         vis = VisualizerWidget(player)
         vis._bars = [7] * BANDS  # pretend mid-animation
 
-        vis.mousePressEvent(None)  # on -> dim
-        vis.mousePressEvent(None)  # dim -> off
+        vis.cycle_mode()  # on -> dim
+        vis.cycle_mode()  # dim -> off
 
         assert vis._mode == MODE_OFF
         assert vis._bars == [0] * BANDS          # blank, not the held frame
@@ -108,7 +108,7 @@ class TestVisualizerToggle:
         player._playing = True
         vis = VisualizerWidget(player)
 
-        vis.mousePressEvent(None)  # on -> dim
+        vis.cycle_mode()  # on -> dim
 
         assert vis._mode == MODE_DIM
         assert vis._timer.isActive()  # dim animates while playing
@@ -119,9 +119,9 @@ class TestVisualizerToggle:
         player._playing = True
         vis = VisualizerWidget(player)
 
-        vis.mousePressEvent(None)  # on -> dim
-        vis.mousePressEvent(None)  # dim -> off
-        vis.mousePressEvent(None)  # off -> on again
+        vis.cycle_mode()  # on -> dim
+        vis.cycle_mode()  # dim -> off
+        vis.cycle_mode()  # off -> on again
 
         assert vis._mode == MODE_ON
         assert vis._timer.isActive()