feat(ios): W0 scaffold + day-1 spike + WireProtocol frozen contract + TestSupport doubles

T-iOS-1: ios/ XcodeGen project (iOS 17, Swift 6 strict concurrency, ATS per PLAN §5.2), 5 SPM package shells, CI skeleton
T-iOS-2: Origin spike vs real server — URLSessionWebSocketTask custom Origin CONFIRMED (no Starscream); 16MiB replay + EMSGSIZE(40) errno correction written back to plan
T-iOS-3: WireProtocol frozen contract, 59 tests, 100% line coverage, cross-impl vectors vs src/protocol.ts via tsx
T-iOS-4: FakeTransport/FakeClock/FakeHTTPTransport doubles
Verify: independent agent re-ran all acceptance — 6/6 PASS

ios/Packages/HostRegistry/Package.swift

@@ -0,0 +1,24 @@
+// swift-tools-version: 6.0
+// T-iOS-1 scaffold shell. Host / HostStore / KeychainHostStore / SecItemShim /
+// InMemoryHostStore / LastSessionStore land in T-iOS-7.
+// Dependency direction is strictly downward: HostRegistry → WireProtocol only.
+import PackageDescription
+
+let package = Package(
+    name: "HostRegistry",
+    platforms: [.iOS(.v17), .macOS(.v14)],
+    products: [
+        .library(name: "HostRegistry", targets: ["HostRegistry"]),
+    ],
+    dependencies: [
+        .package(path: "../WireProtocol"),
+    ],
+    targets: [
+        .target(
+            name: "HostRegistry",
+            dependencies: [.product(name: "WireProtocol", package: "WireProtocol")]
+        ),
+        .testTarget(name: "HostRegistryTests", dependencies: ["HostRegistry"]),
+    ],
+    swiftLanguageModes: [.v6]
+)

ios/Packages/HostRegistry/Sources/HostRegistry/HostRegistryPlaceholder.swift

@@ -0,0 +1,12 @@
+import WireProtocol
+
+/// T-iOS-1 scaffold placeholder.
+///
+/// Real modules land in T-iOS-7: Host, HostStore, KeychainHostStore (via
+/// SecItemShim seam), InMemoryHostStore, LastSessionStore.
+public enum HostRegistryPackage {
+    /// Package identity marker consumed by the scaffold smoke test.
+    public static let packageName = "HostRegistry"
+    /// Proves the single allowed dependency edge (HostRegistry → WireProtocol) compiles.
+    public static let contractPackageName = WireProtocolPackage.packageName
+}

ios/Packages/HostRegistry/Tests/HostRegistryTests/PackageScaffoldTests.swift

@@ -0,0 +1,13 @@
+import Testing
+import HostRegistry
+
+@Test("脚手架:HostRegistry 包可编译且依赖边 HostRegistry→WireProtocol 成立")
+func hostRegistryPackageIsImportableAndDependsOnWireProtocol() {
+    // Arrange / Act
+    let name = HostRegistryPackage.packageName
+    let contract = HostRegistryPackage.contractPackageName
+
+    // Assert
+    #expect(name == "HostRegistry")
+    #expect(contract == "WireProtocol")
+}