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/WebTerm/Wiring/AppCoordinator.swift

@@ -0,0 +1,146 @@
+import Foundation
+import HostRegistry
+import Observation
+import SwiftUI
+
+/// T-iOS-15 · Navigation + lifecycle owner: Pairing → SessionList → Terminal
+/// with the production dependency graph (plan §7 T-iOS-15 step 1).
+///
+/// - Cold start: read the host store once — no paired host → Pairing, else
+///   SessionList (`ColdStartPolicy.initialRoute`).
+/// - `SessionListScreen.onOpen` → build ONE `TerminalSessionController`
+///   (single foreground session, plan §1) and push the terminal.
+/// - Back → `closeTerminal()` → `engine.close()` (detach; PTY keeps running).
+/// - scenePhase is forwarded to the open controller (`.background` →
+///   suspend/close, `.active` → resume/rebuild). The privacy shade is view
+///   layer (RootView + PrivacyShadePolicy), not coordinator state.
+@MainActor
+@Observable
+final class AppCoordinator {
+    private(set) var route: ColdStartPolicy.RootRoute = .loading
+    private(set) var terminalController: TerminalSessionController?
+    /// First-run pairing VM (root route). Recreated per entry to keep pairing
+    /// state machines single-shot.
+    private(set) var rootPairingViewModel: PairingViewModel?
+    /// Add-host pairing VM (sheet from the list header).
+    private(set) var addHostPairingViewModel: PairingViewModel?
+    var isAddHostPresented = false
+
+    let sessionList: SessionListViewModel
+    @ObservationIgnored let environment: AppEnvironment
+
+    init(environment: AppEnvironment) {
+        self.environment = environment
+        sessionList = SessionListViewModel(
+            hostStore: environment.hostStore,
+            http: environment.http,
+            clock: ContinuousClock()
+        )
+    }
+
+    // MARK: - Cold start
+
+    /// Decide the boot route from the host store. A store READ failure routes
+    /// to the session list, whose own `reloadHosts` surfaces the explicit
+    /// error copy (never a silent empty pairing screen hiding a broken store).
+    func bootstrap() async {
+        guard route == .loading else { return }
+        do {
+            let hosts = try await environment.hostStore.loadAll()
+            route = ColdStartPolicy.initialRoute(pairedHostCount: hosts.count)
+        } catch {
+            route = .sessions
+        }
+        if route == .pairing {
+            rootPairingViewModel = makePairingViewModel()
+        }
+    }
+
+    /// First-run pairing done → move to the list (the paired host is already
+    /// in the store — PairingViewModel upserts before signalling).
+    func completeFirstPairing(_ host: HostRegistry.Host) {
+        rootPairingViewModel = nil
+        route = .sessions
+        Task { await sessionList.reloadHosts() }
+    }
+
+    // MARK: - Add-host sheet (list header hook)
+
+    func presentAddHost() {
+        addHostPairingViewModel = makePairingViewModel()
+        isAddHostPresented = true
+    }
+
+    func completeAddHost(_ host: HostRegistry.Host) {
+        isAddHostPresented = false
+        addHostDismissed()
+    }
+
+    /// Sheet gone (paired OR cancelled): drop the VM and refresh hosts — the
+    /// list VM keeps the active host if it still exists.
+    func addHostDismissed() {
+        addHostPairingViewModel = nil
+        Task { await sessionList.reloadHosts() }
+    }
+
+    // MARK: - Terminal open/close
+
+    /// `SessionListScreen.onOpen` (one navigation signal per tap) and the
+    /// "继续上次" banner both land here. `sessionId == nil` = new session.
+    func open(_ request: SessionListViewModel.OpenRequest) {
+        guard terminalController == nil else { return } // one foreground session
+        let controller = TerminalSessionController(
+            host: request.host,
+            sessionId: request.sessionId,
+            environment: environment,
+            onPendingChanged: { [weak self] sessionId, pending in
+                self?.sessionList.setPendingApproval(sessionId: sessionId, pending: pending)
+            }
+        )
+        terminalController = controller
+        controller.start()
+    }
+
+    /// Back navigation popped the terminal: explicit detach.
+    func closeTerminal() {
+        terminalController?.teardown()
+        terminalController = nil
+    }
+
+    // MARK: - "继续上次" (cold start step 5)
+
+    var continueLastSessionId: UUID? {
+        ColdStartPolicy.continueLastSessionId(
+            activeHost: sessionList.activeHost,
+            store: environment.lastSessionStore
+        )
+    }
+
+    func openContinueLast() {
+        guard let host = sessionList.activeHost, let sessionId = continueLastSessionId else {
+            return
+        }
+        open(SessionListViewModel.OpenRequest(id: UUID(), host: host, sessionId: sessionId))
+    }
+
+    // MARK: - scenePhase (plan §7 T-iOS-15 step 3)
+
+    func handleScenePhase(_ phase: ScenePhase) {
+        switch phase {
+        case .background:
+            terminalController?.suspend()
+        case .active:
+            terminalController?.resumeIfNeeded()
+        case .inactive:
+            break // transient; shade covers it at the view layer
+        @unknown default:
+            break
+        }
+    }
+
+    // MARK: - Helpers
+
+    private func makePairingViewModel() -> PairingViewModel {
+        PairingViewModel(store: environment.hostStore, probe: environment.probe)
+    }
+}