fix(display): a non-numeric plugin duration no longer stops the display; narrow scroll strips no longer raise (#739)

* fix(display): a plugin duration that is not a number no longer stops the display

DisplayController._get_display_duration returned whatever the plugin's
get_display_duration() gave back. clock-simple, calendar and countdown
return their display_duration setting straight from config.json, so a
value saved as "20" or null reached _resolve_durations as a string or
None, and its `<= 0` check raised a TypeError. Nothing in the loop caught
it: run()'s outer handler logged "Unexpected error in display controller"
and cleanup() ended the service when that plugin's screen came up, and
systemd restarted it into the same crash.

The plugin's answer is now read as seconds: a finite number or a numeric
string is used (as BasePlugin.get_display_duration already accepts), a
number at or below zero still goes to _resolve_durations' 15 s rule, and
anything else -- None, a non-numeric string, a bool, NaN, infinity, or a
get_display_duration() that raises -- gets the 30 s a mode without a
plugin gets. The warning is logged once per plugin, not at every screen.

Tests: test/test_display_duration_not_a_number.py, including the real
run() on the run-loop harness, which returned at t=30 before the fix.

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

* fix(scroll): a strip narrower than the panel no longer raises on every frame

ScrollHelper._get_visible_portion_integer handled a frame that runs off
the end of the strip by copying the strip's tail and then the rest of the
frame from its head, which assumed the head was at least that wide. For a
strip narrower than the panel that raised "could not broadcast input
array" at every position, so get_visible_portion() never returned a frame
and the caller logged a traceback each frame. Vegas composes such a strip
(lead_in_width defaults to 0) when its content is narrower than the chain.

A wrapping frame is now taken column by column modulo the strip's width
(np.take, mode='wrap', into the reused frame buffer): the tail then the
head, as before, and a narrow strip repeated across the panel. The same
path takes a position before the start of the strip, whose [-n:m] slice
was empty and made frombytes raise; the integer and sub-pixel fast paths
now leave a negative start to it. A zero-width strip is still a black
frame.

Tests: test/test_scroll_helper_narrow_strip.py.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -531,6 +531,25 @@ policies are unchanged.
   for the plugin is refused (`plugin-reloading`), and a config reconcile
   neither loads it twice nor unloads it mid-load. A Vegas fetch that waited
   out a reload for the lock skips the old instance.
+- A plugin display duration that is not a number no longer stops the
+  display. Several plugins (clock-simple, calendar, countdown) return their
+  `display_duration` setting as it is in config.json, so a value saved as
+  `"20"` or `null` (the raw config editor, a hand edit) reached the run loop
+  as a string or None. Comparing it with 0 raised a TypeError that no
+  handler in the loop caught: the display service exited when that plugin's
+  screen came up, and systemd restarted it into the same crash. The
+  controller now reads the plugin's answer as a number: a numeric string
+  counts, and anything else (or a `get_display_duration()` that raises)
+  shows the mode for 30 s, with one warning per plugin.
+- A scroll strip narrower than the panel scrolls instead of raising on every
+  frame. When a frame ran off the end of the strip, `ScrollHelper` copied
+  the strip's tail and then the rest of the frame from its head, which
+  assumed the head was that wide; for a narrower strip that raised
+  `ValueError: could not broadcast` at every position, so nothing was drawn
+  and each frame logged a traceback. Vegas builds such a strip, with no
+  lead-in, when its content is narrower than the chain. A frame that runs
+  off the strip now continues from its head column by column, so a narrow
+  strip repeats across the panel; a wide strip wraps exactly as before.
 - The schedule-off blank and the WiFi notice no longer start with a
   scroller's leftovers. Both are drawn by the display controller rather than
   dispatched to a plugin, so #716's handover never reached them: drawn while