banner: explicit opacity fade (transitions were unreliable)

SwiftUI's removal transition never actually played despite .id keying — the
tip banner vanished instantly on dismiss. Replace it with explicit opacity/
offset driven by withAnimation in reflectBanner (gated by a .task(id:
activeBanner) so presentation is reliable and prompt): a dismissal now
fades out + slides up over 0.35s, and a tip→network swap crossfades. Uses
the same state-driven pattern that fixed the HermesCall ticker fades.

FuelBoard/ContentView.swift

@@ -84,6 +84,16 @@ struct ContentView: View {
     /// network/offline strip (ContentView renders it above the tabs).
     @StateObject private var tipStore = TipStore()
 
+    // --- Explicit banner animation state (robust fade-out) ---
+    // SwiftUI's removal transition for the banner proved unreliable here
+    // (the tip faded to nothing only in the cross-nil case, and even then
+    // inconsistently). Drive opacity/offset explicitly instead so a
+    // dismissal ALWAYS fades + slides up on ANY banner change.
+    @State private var currentBanner: AppBanner?
+    @State private var bannerOpacity: Double = 0
+    @State private var bannerOffset: CGFloat = 0
+    @State private var bannerClearTask: Task<Void, Never>?
+
     /// The pool the list draws from. In Cheapest mode the chosen miles radius
     /// bounds it ("best price within X miles"); in Closest mode the radius is
     /// redundant — the whole country sorted nearest-first, because "nearest"
@@ -485,26 +495,75 @@ struct ContentView: View {
         GeometryReader { geo in
             ZStack(alignment: .top) {
                 rootTabView
-                if let banner = activeBanner {
+                if let banner = currentBanner {
                     // Floating near the top of the screen, over the nav area —
                     // overlays content (never pushes it) and sits above the
                     // main content so it doesn't cover or block the list/pill
-                    // beneath it.
+                    // beneath it. Opacity/offset are driven explicitly by
+                    // reflectBanner so the fade-out reliably animates.
                     floatingBanner(banner)
-                        // Key by value so ANY change (tip→network, tip→nil)
-                        // runs the removal transition (fade/slide-out) instead
-                        // of silently swapping content in place.
-                        .id(banner)
                         .padding(.top, geo.safeAreaInsets.top + 10)
-                        .transition(.asymmetric(
-                            insertion: .move(edge: .top).combined(with: .opacity),
-                            // Slide up + fade on dismiss/timeout (one style for all).
-                            removal: .move(edge: .top).combined(with: .opacity)
-                        ))
+                        .opacity(bannerOpacity)
+                        .offset(y: bannerOffset)
                 }
             }
         }
-        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: activeBanner)
+        .task(id: activeBanner) {
+            // Fires on launch with the current banner AND whenever it changes —
+            // unlike onChange(computed) which can miss the first non-nil value
+            // when dataStatus is set slightly after the view appears.
+            reflectBanner(activeBanner)
+        }
+    }
+
+    /// Explicitly animates the banner in/out — a robust replacement for the
+    /// SwiftUI removal transition (which was silently not firing). Handles:
+    ///  - first appearance → fade + settle down from slightly above
+    ///  - any content change (tip→network, new tip) → fade the old out, then
+    ///    fade the new in — so a tip ALWAYS visibly fades away
+    ///  - dismissal → fade out + slide up, then clear after the fade
+    private func reflectBanner(_ newBanner: AppBanner?) {
+        guard newBanner != currentBanner else { return }
+        bannerClearTask?.cancel()
+        if let newBanner {
+            if currentBanner == nil {
+                present(newBanner)
+            } else {
+                // Crossfade: slide+fade the current out, then present the new.
+                withAnimation(.easeOut(duration: 0.2)) {
+                    bannerOpacity = 0
+                    bannerOffset = -28
+                }
+                bannerClearTask = Task { @MainActor in
+                    try? await Task.sleep(nanoseconds: 250_000_000)
+                    guard !Task.isCancelled else { return }
+                    present(newBanner)
+                }
+            }
+        } else {
+            withAnimation(.easeOut(duration: 0.35)) {
+                bannerOpacity = 0
+                bannerOffset = -28
+            }
+            bannerClearTask = Task { @MainActor in
+                try? await Task.sleep(nanoseconds: 350_000_000)
+                guard !Task.isCancelled else { return }
+                currentBanner = nil
+                bannerOpacity = 0
+                bannerOffset = 0
+            }
+        }
+    }
+
+    /// Fade a banner in from slightly above and settle it into place.
+    private func present(_ banner: AppBanner) {
+        currentBanner = banner
+        bannerOpacity = 0
+        bannerOffset = -16
+        withAnimation(.easeOut(duration: 0.3)) {
+            bannerOpacity = 1
+            bannerOffset = 0
+        }
     }
 
     private var rootTabView: some View {