fix(vegas): a display duration that is not a number no longer cancels a static pause

The Vegas static pause compared plugin.get_display_duration() with the
clock. clock-simple, calendar and countdown return their display_duration
setting straight from config.json, so a value saved as "20" or null
reached that comparison as a string or None. The TypeError went to the
pause's broad except, which ended the pause: the plugin flashed up and
the scroll went straight on, at every one of its turns. inf held the
pause until something interrupted it, and NaN, False, 0 or a negative
number ended it at once.

The pause now reads the duration the way the rotation has since #739,
with the same helper, then the rotation's fallbacks: 30 s for anything
that is not a number or a get_display_duration() that raises, 15 s for a
number at or below zero. Logged once per plugin. test_vegas_static_mode.py's
pauses used 0 to mean "no wait"; they now use 0.01.

The helper moves from display_controller (_finite_seconds) to base_plugin
(finite_seconds), unchanged: the coordinator cannot import from
display_controller, which imports src.vegas_mode at module level, and a
new src module would turn ledmatrix-plugins' min-core table check red
until it was listed. base_plugin is already loaded whenever either one is.

Tests: test/test_vegas_static_pause_duration.py, on a fake clock,
including TestSameAsTheRotation, which runs every value through both the
pause and the rotation's _get_display_duration/_resolve_durations.

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

CHANGELOG.md

@@ -885,6 +885,18 @@ policies are unchanged.
   a runtime publisher that stops still goes `stale`, and a subscription that
   goes quiet still falls back to the cache. The cache path's 120 s rule is
   unchanged.
+- A plugin that pauses the Vegas scroll gets its pause when its display
+  duration is not a plain number. Several plugins (clock-simple, calendar,
+  countdown) return `display_duration` as it is in config.json, so a value
+  saved as `"20"` or `null` (the raw config editor, a hand edit) reached the
+  pause as a string or None; comparing it with the clock raised, and the
+  plugin flashed up and the scroll went straight on, at every one of its
+  turns. `inf` held the pause until something interrupted it, and 0, a
+  negative number or NaN ended it at once. The pause now reads the duration
+  as the rotation does (`finite_seconds()` in `base_plugin`): a numeric
+  string counts, anything else that is not a finite number (or a
+  `get_display_duration()` that raises) pauses for 30 s, and a number at or
+  below zero for 15 s, with one warning per plugin.
 
 ### Scrolling