Update FuelBoard onboarding copy, title formatting, key sheet card wrapping, and best-value button placement

FuelBoard/FuelSavingsViews.swift

@@ -78,6 +78,7 @@ struct FuelSavingsSummaryView: View {
     /// Sizes the "extra return travel" caption in the user's own unit (the
     /// stored figure is miles) — used by both the row banner and the detail sheet.
     var distanceUnit: DistanceUnit = .miles
+    var showInfoAction: (() -> Void)? = nil
 
     var body: some View {
         switch availability {
@@ -166,6 +167,22 @@ struct FuelSavingsSummaryView: View {
                             .font(.caption2)
                             .foregroundStyle(.secondary)
                     }
+                    if let showInfoAction {
+                        Rectangle()
+                            .fill(Color(.separator))
+                            .frame(height: 0.5)
+                            .padding(.vertical, 4)
+                        Button(action: showInfoAction) {
+                            HStack(spacing: 8) {
+                                Text("How Best Value works")
+                                Spacer(minLength: 8)
+                                Image(systemName: "chevron.forward")
+                                    .font(.footnote.weight(.semibold))
+                                    .foregroundStyle(.tertiary)
+                            }
+                        }
+                        .buttonStyle(.plain)
+                    }
                 }
             }
         case .unavailable(let reason):