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>

test/fixtures/run_loop_golden/vegas.json

@@ -3,8 +3,8 @@
     [0.0, "<vegas>", 30.008, "duration", 3751, null],
     [30.008, "<vegas>", 30.007, "duration", 3751, null],
     [60.015, "<vegas>", 10.24, "vegas-live", 1280, null],
-    [70.255, "clock", 20.0, "duration", 20, false],
-    [90.255, "sports_live", 20.0, "display-false", 11, true],
+    [70.255, "sports_live", 20.0, "duration", 20, true],
+    [90.255, "sports_live", 20.0, "display-false", 11, false],
     [110.255, "<vegas>", 30.008, "duration", 3751, null],
     [140.263, "<vegas>", 10.0, "on-demand-start", 1250, null],
     [150.263, "clock", 20.0, "duration", 20, true],
@@ -16,6 +16,7 @@
   ],
   "events": [
     [70.255, "vegas-live"],
+    [70.255, "live", "sports_live"],
     [150.0, "request", "start:v1"],
     [150.263, "on-demand-start", "clock"],
     [150.263, "vegas-interrupt"],