fix(ios): 3 architecture bugs surfaced by real-iPhone device test

End-to-end verification on a connected iPhone 17 Pro Max via CoreDevice
tunnel exposed three bugs the TS-stubbed and macOS-XCTest layers missed:

1. acceptLocalOnly=true was too tight. Network.framework's "local" gate
   only allows ::1 / 127.0.0.1, silently dropping CoreDevice tunnel peers
   (the very transport the architecture is designed for). The device log
   showed "Ignoring non-local connection from fd72:8347:2ead::2" — the
   Mac's tunnel-side address. Replaced with explicit per-connection ULA
   gate (RFC 4193 fc00::/7) in isLoopbackPeer.

2. DebugBridgeCore (Foundation+Network) referenced DebugOverlayWindow
   which lives in DebugBridgeUI (UIKit). Backwards module dep. Compiled
   on macOS only because canImport(UIKit) stripped it; broke on iOS.
   Moved the overlay install responsibility to the consuming app's
   wiring (DebugBridgeWiring.swift.template already shows the pattern).

3. @Observable macro + @Snapshotable property wrapper conflict. Both
   try to synthesize backing storage; can't coexist on the same property.
   The production guidance is: nest snapshot-eligible state in a struct
   inside an ObservableObject (or use the canonical-state-struct atomicity
   strategy). Fixture switched to a plain class to demonstrate.

Smoke loop on the real device now passes 7/8 endpoints:
- /healthz (200), /tap unauth (401), /auth/rotate (200), boot-token reuse
  rejected (401), /session/acquire (200), /state/snapshot (200 with schema
  envelope), /session/release (200). /tap with valid session returns 200
  HTTP + op:false because the FixtureApp doesn't wire MutationBridge.resolver
  to a real UI tap — expected for a minimal fixture; the production wiring
  template handles it.

Also adds:
- test/fixtures/ios-qa/FixtureApp/Sources/FixtureApp/FixtureAppApp.swift
  (SwiftUI @main entry that boots StateServer)
- test/fixtures/ios-qa/FixtureApp/Sources/FixtureApp/Info.plist
- test/fixtures/ios-qa/FixtureApp/project.yml (xcodegen project spec
  with DEVELOPMENT_TEAM 623FYQ2M88, bundle id com.gstack.iosqa.fixture)

End-to-end verified path:
  xcodegen generate
  xcodebuild -allowProvisioningUpdates -allowProvisioningDeviceRegistration
  devicectl device install app
  devicectl device process launch
  devicectl device copy from --source tmp/gstack-ios-qa.token
  curl -6 http://[<corodevice-ipv6>]:9999/...

ios-qa/templates/DebugBridgeManager.swift.template

@@ -1,19 +1,20 @@
 // AUTO-GENERATED from gstack/ios-qa/templates/DebugBridgeManager.swift.template
 //
-// Bootstraps StateServer + DebugOverlay on app launch. Reads the codegen
-// output, registers accessors, and starts the listeners. Everything is
-// #if DEBUG-gated; this file does not exist in Release builds.
+// Bootstraps StateServer on app launch. Lives in DebugBridgeCore (no UIKit
+// dependency). The DebugOverlay install is wired separately by the consuming
+// app — it lives in DebugBridgeUI which depends on DebugBridgeCore (not the
+// other way around). Everything is #if DEBUG-gated; this file does not exist
+// in Release builds.
 
 #if DEBUG
 
 import Foundation
-import SwiftUI
 
 @MainActor
 public final class DebugBridgeManager {
     public static let shared = DebugBridgeManager()
 
-    public func start(appState: AppState, recording: Bool = false) {
+    public func start(appState: AppState) {
         // 1. Register the canonical AppState struct + accessor wiring.
         //    AppStateAccessor.register(_:) is generated by gen-accessors-tool.
         AppStateAccessor.register(appState)
@@ -21,10 +22,12 @@ public final class DebugBridgeManager {
         // 2. Boot the StateServer.
         StateServer.shared.start()
 
-        // 3. Install the DebugOverlay window.
-        #if canImport(UIKit)
-        DebugOverlayWindow.shared.install(recording: recording)
-        #endif
+        // 3. The consuming app installs DebugOverlayWindow separately. See
+        //    the example in DebugBridgeWiring.swift.template:
+        //
+        //      #if canImport(UIKit)
+        //      DebugOverlayWindow.shared.install(recording: recording)
+        //      #endif
     }
 }