A/B test: from-scratch minimal small widget (proven medium intent)

Temporary FuelBoardTestSmallWidget kind: a small-face widget driven by
the PROVEN medium intent (fuel/sort/distance only — no favourite params,
no dependency, no custom entity query), registered first in the gallery.
Isolates small SIZE vs small INTENT: if it populates while
FuelPriceSmallWidget skeletons, the small intent's extra machinery is the
culprit; if it also skeletons, the failure is small-family/system-level.
Provider gains a beaconTag so the test widget's beacons are
distinguishable in the relay log and keychain slots. Removed once the
root cause is confirmed.

FuelBoardWidgets/FuelBoardWidgetsBundle.swift

@@ -4,7 +4,10 @@ import SwiftUI
 @main
 struct FuelBoardWidgetsBundle: WidgetBundle {
     var body: some Widget {
-        // Gallery order follows registration order: small first, then medium.
+        // Gallery order follows registration order. The A/B test widget is
+        // first so it's easy to find; remove it once the small-widget root
+        // cause is confirmed.
+        FuelBoardTestSmallWidget()
         FuelPriceSmallWidget()
         FuelPriceWidget()
         FuelBoardLiveActivity()