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/URLSessionHTTPTransport.swift

@@ -0,0 +1,26 @@
+import Foundation
+import WireProtocol
+
+/// T-iOS-15 · Production `HTTPTransport` (the WireProtocol seam's doc reserves
+/// the URLSession wrapper for the production side; no package owns it, so the
+/// assembly layer provides it). Deliberately logic-free: `APIClient` builds
+/// every request — including the Origin-iff-G rule (plan §3.4 铁律) — and this
+/// type only performs the exchange. Adding ANY header/URL logic here would
+/// bypass that single audited point (review CRITICAL).
+struct URLSessionHTTPTransport: HTTPTransport {
+    private let session: URLSession
+
+    init(session: URLSession = .shared) {
+        self.session = session
+    }
+
+    func send(_ request: URLRequest) async throws -> (Data, HTTPURLResponse) {
+        let (data, response) = try await session.data(for: request)
+        guard let httpResponse = response as? HTTPURLResponse else {
+            // http(s)-only endpoints (HostEndpoint validates) always produce
+            // an HTTPURLResponse; anything else is a transport-level anomaly.
+            throw URLError(.badServerResponse)
+        }
+        return (data, httpResponse)
+    }
+}