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_round29.py

@@ -900,8 +900,8 @@ class TestTransportLayout:
         vis = bar._visualizer
         before = vis._mode
 
-        # Not casting: a click still cycles the brightness as it always did.
-        vis.mousePressEvent(None)
+        # Not casting: the colour wheel cycles the brightness.
+        vis.cycle_mode()
         assert vis._mode != before
         cast.disconnect.assert_not_called()
 
@@ -1020,4 +1020,4 @@ class TestVisualizerWhileCasting:
         assert "click to stop" in vis.toolTip()
 
         player.set_sink(None)
-        assert "cycle" in vis.toolTip()        # back to the brightness control
+        assert "big" in vis.toolTip()          # back to the tile's own tooltip