test(ios): real Swift compile + XCTest fixture; device-path probe; loopback bind fix

Closes the gap from prior commits where E2E tests stubbed the Swift StateServer
in TypeScript. Now there's a real SwiftPM fixture at test/fixtures/ios-qa/FixtureApp/
that compiles the production templates and runs an XCTest suite against the
actual StateServer implementation. Three new test layers:

- swift build invariants (periodic-tier): debug-config build succeeds, XCTest
  suite passes (validates real Swift impl over Foundation + Network), release-config
  build has zero DebugBridge symbols (structural #if DEBUG gate works end-to-end).

- Real-device probe (periodic-tier, GSTACK_HAS_IOS_DEVICE=1): devicectl can list
  + pair the connected iPhone. Surfaces actionable instructions when the trust
  dialog hasn't been confirmed yet.

- Fixture sources copied from ios-qa/templates/ — Package.swift splits the
  bridge into DebugBridgeCore (Foundation+Network, cross-platform) and
  DebugBridgeUI (UIKit/SwiftUI, iOS-only) so swift build can validate the
  bulk of the production code on macOS without an iPhone or simulator.

Also fixes a real bug the XCTest unit suite caught: NWListener with
requiredLocalEndpoint on params silently fails to bind for listening (it's
an outbound-connection concept). Replaced with .requiredInterfaceType=.loopback
+ .acceptLocalOnly=true + a per-connection peer-address check. The fork's
inherited code had this bug; we shipped it untouched in v1.41.0.0 and the
new XCTest suite caught it immediately.

test/fixtures/ios-qa/FixtureApp/Package.swift

@@ -0,0 +1,41 @@
+// swift-tools-version:5.9
+// Test fixture: minimal SwiftUI app + DebugBridge SPM package.
+// DebugBridgeCore (Foundation+Network) builds cross-platform.
+// DebugBridgeUI (UIKit/SwiftUI) is iOS-only.
+
+import PackageDescription
+
+let package = Package(
+    name: "FixtureApp",
+    platforms: [
+        .iOS(.v16),
+        .macOS(.v13),
+    ],
+    products: [
+        .library(name: "DebugBridgeCore", targets: ["DebugBridgeCore"]),
+        .library(name: "DebugBridgeUI", targets: ["DebugBridgeUI"]),
+    ],
+    targets: [
+        .target(
+            name: "DebugBridgeCore",
+            dependencies: [],
+            path: "Sources/DebugBridgeCore",
+            swiftSettings: [
+                .define("DEBUG", .when(configuration: .debug)),
+            ]
+        ),
+        .target(
+            name: "DebugBridgeUI",
+            dependencies: ["DebugBridgeCore"],
+            path: "Sources/DebugBridgeUI",
+            swiftSettings: [
+                .define("DEBUG", .when(configuration: .debug)),
+            ]
+        ),
+        .testTarget(
+            name: "DebugBridgeCoreTests",
+            dependencies: ["DebugBridgeCore"],
+            path: "Tests/DebugBridgeCoreTests"
+        ),
+    ]
+)