refactor: migrate iOS gateway to unified ws

apps/shared/ClawdbotKit/Sources/ClawdbotKit/GatewayPayloadDecoding.swift

@@ -0,0 +1,20 @@
+import ClawdbotProtocol
+import Foundation
+
+public enum GatewayPayloadDecoding {
+    public static func decode<T: Decodable>(
+        _ payload: ClawdbotProtocol.AnyCodable,
+        as _: T.Type = T.self) throws -> T
+    {
+        let data = try JSONEncoder().encode(payload)
+        return try JSONDecoder().decode(T.self, from: data)
+    }
+
+    public static func decodeIfPresent<T: Decodable>(
+        _ payload: ClawdbotProtocol.AnyCodable?,
+        as _: T.Type = T.self) throws -> T?
+    {
+        guard let payload else { return nil }
+        return try self.decode(payload, as: T.self)
+    }
+}