feat(ios): W4 app wiring — DI graph, event fan-out, lifecycle, privacy shade

T-iOS-15: AppEnvironment production DI (real Keychain/probe/transports), EventFanOut
(engine.events → TerminalVM + GateVM + activity bridge), scenePhase lifecycle
(.background→close, suspend→rebuild+reopen reclaims size), privacy shade on != .active,
spike screen deleted, cold-start routing
Walkthrough proxies: hosted live-server smoke over the production DI graph (probe→store→
attach→echo→close) + real-Keychain kSecAttrAccessible assertion (closes T-iOS-7 deferral)
Deviation closed: TerminalViewModel.lastSentDims (valid-only) + alive-engine .active →
notifyForegrounded(dims:) (orchestrator fix on behalf of T-iOS-11 owner)
Env finding: repo under ~/Documents → TCC blocks sim-spawned node; SimServerHarness dual-mode
(self-bootstrap / WEBTERM_SERVER_URL via simctl launchctl setenv)
Verified: 214 pkg + 76 app + 10 integration tests green; verify agent 8/8 PASS

ios/App/WebTermTests/PrivacyShadeTests.swift

@@ -0,0 +1,29 @@
+import SwiftUI
+import Testing
+@testable import WebTerm
+
+/// T-iOS-15 · Privacy-shade state mapping (plan §7 T-iOS-15, security-critical).
+///
+/// The rule under test is EXACT: the shade covers whenever
+/// `scenePhase != .active` — NOT just `.inactive`. Entering the app switcher
+/// is `.inactive`, but the moment iOS writes the switcher snapshot to disk is
+/// `.background`; covering only one of the two leaks terminal content
+/// (API keys / tokens / source) into the on-disk snapshot.
+@MainActor
+@Suite("PrivacyShadePolicy")
+struct PrivacyShadeTests {
+    @Test("scenePhase == .active → 遮罩隐藏（恢复终端）")
+    func activeShowsTerminal() {
+        #expect(!PrivacyShadePolicy.isShadeVisible(for: .active))
+    }
+
+    @Test("scenePhase == .inactive → 遮罩可见（切换器入口态）")
+    func inactiveIsCovered() {
+        #expect(PrivacyShadePolicy.isShadeVisible(for: .inactive))
+    }
+
+    @Test("scenePhase == .background → 遮罩可见（快照写盘时刻）")
+    func backgroundIsCovered() {
+        #expect(PrivacyShadePolicy.isShadeVisible(for: .background))
+    }
+}