fix(display): live games take over within a second, and straight from Vegas (#713)

A game that goes live takes over within about a second (_check_live_takeover in the frame loops and the dwell sleep, throttled to 1 s, never during on-demand, scheduled-off, live_in_ticker or an already-live screen); an interrupted Vegas iteration switches straight to the game; has_live_content() is asked once per plugin per scan. Goldens: live_priority, vegas.

Merged with #712: after an interrupted Vegas iteration the WiFi-notice check runs before the live switch (WiFi outranks live). Adds test/test_run_loop_wifi_and_live.py, pinning that a notice and a game arriving during the same screen (1 Hz, 125 Hz, Vegas) show the notice first, then the game, and neither while scheduled off.

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

CHANGELOG.md

@@ -101,6 +101,15 @@ policies are unchanged.
   notice is what shows next, and Vegas resumes after it; before, a rotation
   screen showed instead and the notice expired behind it. An active
   on-demand session still holds the panel until it ends.
+- A game that goes live now takes over the panel within about a second.
+  Live priority was only checked between screens, so a game that went live
+  during a 30 s screen waited for that screen to end. The frame loops and the
+  dwell sleep now check too, at most once a second, and not while an
+  on-demand session is running or a live game is already showing. When Vegas
+  stops for a live game, the game is the next screen. Before, one rotation
+  screen showed first and the game came after it. Each check also asks each
+  plugin `has_live_content()` once, where a plugin registered under several
+  modes used to be asked once per mode.
 
 ## 3.8.0