fix(sports): scroll and Vegas cards name the printed date's own weekday (#747)

With scroll_card.date_format "weekday", a Friday 8 PM ET game read
"Sat Oct 2" on the scroll and Vegas cards.

Cause: the extractor prints the "M/D" in the plugin's resolved zone (its
own setting, then the global one, then the system zone), but the card is
handed only the plugin's config. Its timezone ships as "", so
card_tzinfo fell back to UTC and the weekday belonged to the UTC date:
the next day for evening games in the Americas, the previous day for
morning games east of UTC (Auckland, Kiritimati).

Fix: every zone is within a day of UTC, so the printed date is the
start's UTC date or a neighbour of it. _format_date_as now takes the game
and names the weekday of whichever of those days has the printed month
and day, falling back to the zone-based weekday only when the start
cannot place the date (no offset, unparseable, or more than a day away).
The switch-mode scorebug shares the formatter and passes the game too, so
the twins stay identical; it already used the resolved zone and draws
what it drew before. Public signatures are unchanged.

Tests cover US DST end, New Year's Eve, both sides of the date line, NZ
DST start and UTC+14. The twins test's weekday pin is updated: the drawn
date now agrees, and only the bare weekday helpers still differ.

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

CHANGELOG.md

@@ -699,6 +699,17 @@ policies are unchanged.
   heartbeat when the service stops), is `stale` at once instead of `live`
   for up to 180 s. No new files or writes: both checks are on the reading
   side.
+- A scoreboard's scroll and Vegas cards with `scroll_card.date_format:
+  "weekday"` now show the printed date's own weekday. A Friday 8 PM ET game
+  read "Sat Oct 2". The card took the weekday in the plugin's own
+  `timezone` setting, which ships blank, so it fell back to UTC, while the
+  "Oct 2" beside it came from the zone the plugin actually resolves (its
+  setting, then the global one, then the system zone). Every zone is within a
+  day of UTC, so the card now finds which day near the start's UTC date has
+  the printed month and day and names that one. Games east of UTC (Auckland,
+  Kiritimati) were off by a day the other way and are fixed the same way.
+  The switch-mode scorebug, which already used the plugin's resolved zone,
+  shares the same formatter and draws what it drew before.
 - `/api/v3/display/current-status` reflects a wake from scheduled-off, a
   schedule-off blank, or an on-demand session starting or ending at once,
   even when the mode name stays the same. The display republished its