fix(vegas): a static pause redraws its plugin for the whole pause

The pause called display(force_clear=True) once and slept out the
duration, so a plugin that rotates its screens or animates (Fantasy
Blitz's playlist) was frozen on its first frame. The pause now calls
display() again at the rotation's rate: once a second, or the high-FPS
interval for a plugin that declares needs_high_fps (or scrolls). Only
the first call clears. A redraw that finds update() holding the plugin
lock is skipped; the pause carries on. Interrupt checks and the
watchdog beat still run every 0.1 s; a raise still ends the pause.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/test_vegas_static_pause_duration.py

@@ -19,7 +19,7 @@ import logging
 import os
 import threading
 from types import SimpleNamespace
-from unittest.mock import MagicMock
+from unittest.mock import MagicMock, call
 
 os.environ.setdefault("EMULATOR", "true")
 
@@ -62,6 +62,7 @@ def _plugin(duration, plugin_id='clock-simple'):
     plugin = MagicMock()
     plugin.plugin_id = plugin_id
     plugin.get_display_duration.return_value = duration
+    plugin.needs_high_fps = False
     return plugin
 
 
@@ -104,7 +105,9 @@ class TestPauseLength:
         completed, lasted = _pause(_coord(plugin), plugin, clock)
         assert completed is True
         assert lasted == pytest.approx(30.0, abs=0.15)
-        plugin.display.assert_called_once_with(force_clear=True)
+        # Redrawn once a second; only the first draw clears.
+        assert plugin.display.call_args_list[0] == call(force_clear=True)
+        assert plugin.display.call_count == 30
 
     @pytest.mark.parametrize('value', NOT_ABOVE_ZERO, ids=repr)
     def test_a_number_not_above_zero_pauses_for_15s(self, clock, value):