Add local Live Activity and Dynamic Island track display

Shared/MusicActivityAttributes.swift

@@ -0,0 +1,26 @@
+import ActivityKit
+import Foundation
+
+struct MusicActivityAttributes: ActivityAttributes {
+    struct ContentState: Codable, Hashable {
+        var title: String
+        var artist: String
+        var playing: Bool
+        var position: Double
+        var duration: Double
+        var updatedAt: Date
+        var connected: Bool
+
+        // Bound UTF-8, including pathological combining characters, below ActivityKit's 4 KB limit.
+        static func bounded(_ text: String) -> String {
+            var result = ""
+            for scalar in text.unicodeScalars {
+                guard result.utf8.count + scalar.utf8.count <= 256 else { break }
+                result.unicodeScalars.append(scalar)
+            }
+            return result
+        }
+
+        var progress: Double { duration > 0 ? min(1, max(0, position / duration)) : 0 }
+    }
+}