chore: import upstream snapshot with attribution

ios/Sources/JCodeKit/Pairing.swift

@@ -0,0 +1,77 @@
+import Foundation
+
+/// Exchanges a pairing code for a long-lived auth token via `POST /pair`.
+public struct PairingClient: Sendable {
+    public struct Response: Equatable, Sendable {
+        public var token: String
+        public var serverName: String
+        public var serverVersion: String
+
+        public init(token: String, serverName: String, serverVersion: String) {
+            self.token = token
+            self.serverName = serverName
+            self.serverVersion = serverVersion
+        }
+    }
+
+    public enum PairingError: Error, Equatable {
+        case invalidCode(String)
+        case serverError(statusCode: Int, message: String)
+        case invalidResponse
+    }
+
+    private let session: URLSession
+
+    public init(session: URLSession = .shared) {
+        self.session = session
+    }
+
+    public func pair(
+        gateway: Gateway,
+        code: String,
+        deviceID: String,
+        deviceName: String
+    ) async throws -> Response {
+        var request = URLRequest(url: gateway.pairURL)
+        request.httpMethod = "POST"
+        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
+        request.timeoutInterval = 15
+        let body: [String: String] = [
+            "code": code,
+            "device_id": deviceID,
+            "device_name": deviceName,
+        ]
+        request.httpBody = try JSONSerialization.data(withJSONObject: body)
+
+        let (data, response) = try await session.data(for: request)
+        guard let http = response as? HTTPURLResponse else {
+            throw PairingError.invalidResponse
+        }
+        let object = (try? JSONSerialization.jsonObject(with: data)) as? [String: Any] ?? [:]
+        guard http.statusCode == 200 else {
+            let message = object["error"] as? String ?? "HTTP \(http.statusCode)"
+            if http.statusCode == 401 {
+                throw PairingError.invalidCode(message)
+            }
+            throw PairingError.serverError(statusCode: http.statusCode, message: message)
+        }
+        guard let token = object["token"] as? String, !token.isEmpty else {
+            throw PairingError.invalidResponse
+        }
+        return Response(
+            token: token,
+            serverName: object["server_name"] as? String ?? "jcode",
+            serverVersion: object["server_version"] as? String ?? "unknown"
+        )
+    }
+
+    /// Probes `GET /health`. Returns true when the gateway is reachable.
+    public func checkHealth(gateway: Gateway) async -> Bool {
+        var request = URLRequest(url: gateway.healthURL)
+        request.timeoutInterval = 5
+        guard let (_, response) = try? await session.data(for: request),
+            let http = response as? HTTPURLResponse
+        else { return false }
+        return http.statusCode == 200
+    }
+}