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>

src/plugin_system/base_plugin.py

@@ -11,6 +11,7 @@ Stability: Stable - maintains backward compatibility
 from abc import ABC, abstractmethod
 from enum import Enum
 from typing import Dict, Any, Optional, List
+import math
 import os
 import sys
 from src.deprecation import deprecated, warn_deprecated
@@ -240,6 +241,26 @@ def resolve_vegas_participation(plugin: Any, plugin_id: Optional[str] = None) ->
     return legacy_vegas_participation(plugin)
 
 
+def finite_seconds(value: Any) -> Optional[float]:
+    """``value`` as seconds when it is a finite number or a numeric string,
+    else None. A bool is not a number here, though it is an int: True would
+    read as a one-second screen.
+
+    How the core reads a plugin's get_display_duration() -- the rotation
+    (DisplayController._get_display_duration) and the Vegas static pause --
+    which several plugins answer straight from config.json, so a value saved
+    as "20" or null arrives as a string or None. A number at or below zero is
+    returned as it is; each caller has its own rule for that.
+    """
+    if isinstance(value, bool):
+        return None
+    try:
+        seconds = float(value)
+    except (TypeError, ValueError, OverflowError):
+        return None
+    return seconds if math.isfinite(seconds) else None
+
+
 class BasePlugin(ABC):
     """
     Base class that all plugins must inherit from.