WIP: local handoff implementation

Local work on the social.io handoff before merging the claude
worktree branch. Includes the full per-spec Sources/Core/Design
module (8 files), watchOS target under WatchApp/, Live Activity +
widget extension, entitlements, scheme, and asset catalog.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

swift/Sources/Core/Design/Haptics.swift

@@ -0,0 +1,25 @@
+import SwiftUI
+
+#if os(iOS)
+import UIKit
+#endif
+
+enum Haptics {
+    static func selection() {
+        #if os(iOS)
+        UISelectionFeedbackGenerator().selectionChanged()
+        #endif
+    }
+
+    static func success() {
+        #if os(iOS)
+        UINotificationFeedbackGenerator().notificationOccurred(.success)
+        #endif
+    }
+
+    static func warning() {
+        #if os(iOS)
+        UINotificationFeedbackGenerator().notificationOccurred(.warning)
+        #endif
+    }
+}