Initial scaffold: context-aware notes app for iOS + macOS

XcodeGen project (Notes / NotesMac / NotesTests), Swift 6 strict concurrency,
iCloud-document storage via IndieSync with a SwiftData cache, automatic
capture context (location, place, time zone, device) on every note,
context-based relevance ranking with a 'Right here, right now' shelf,
tags, search, and the square.and.pencil-on-red app icon.

Notes/Views/App/ICloudGateView.swift

@@ -0,0 +1,28 @@
+import SwiftUI
+
+/// Blocking screen when the ubiquity container can't be obtained. The app
+/// deliberately has no local-only fallback — notes written without iCloud
+/// would exist nowhere durable and be wiped by the next cache rebuild.
+struct ICloudGateView: View {
+    @Environment(SyncEngine.self) private var syncEngine
+
+    var body: some View {
+        VStack(spacing: 16) {
+            Image(systemName: "icloud.slash")
+                .font(.system(size: 56))
+                .foregroundStyle(.secondary)
+            Text("iCloud Required")
+                .font(.title2.bold())
+            Text("Notes stores everything in your iCloud Drive so it's on all your devices. Sign in to iCloud and enable iCloud Drive for Notes in Settings, then try again.")
+                .font(.callout)
+                .foregroundStyle(.secondary)
+                .multilineTextAlignment(.center)
+                .frame(maxWidth: 420)
+            Button("Try Again") {
+                Task { await syncEngine.connect() }
+            }
+            .buttonStyle(.borderedProminent)
+        }
+        .padding(32)
+    }
+}