feat(ipad): W1-W3 — adaptive split-view layout + finding fixes

T-iPad-2: AdaptiveRootView/LayoutPolicy (sole size-class decision), SplitRootView
(NavigationSplitView sidebar+detail), StackRootView (iPhone path verbatim, zero
regression); privacy shade hoisted to shared ZStack top for both branches
T-iPad-3: KeyBarVisibility predicate (hide when hardware keyboard present),
pointer context menu (copy/new-in-cwd/kill, all via existing channels)
T-iPad-4: Projects multi-column grid on iPad (idiom-gated), adaptive sheet detents
T-iPad-5 findings (4/4 fixed): kill onKillSession thread-through +
AppCoordinator.killCurrentSession; split route-gated to .sessions (iPad first-run
pairing); continue-last banner in split sidebar; iPad XCUITest deferred (covered
by SidebarSelectionTests)
Verified: iPhone 16 277 + iPad Pro 11 278 tests green; packages 261 + integration 10;
zero changes under ios/Packages, src/, public/

ios/App/WebTerm/Wiring/AppCoordinator.swift

@@ -170,6 +170,62 @@ final class AppCoordinator {
         terminalController = nil
     }
 
+    /// T-iPad-3 · 终端指针上下文菜单「结束会话」→ 复用既有 kill 通道
+    /// （`SessionListViewModel.kill` → `APIClient.killSession`，带 Origin，无新
+    /// 网络路径），随后 detach detail。无 adopted 会话 → no-op。
+    func killCurrentSession() {
+        guard let sessionId = terminalController?.terminalViewModel.sessionId else { return }
+        Task { await sessionList.kill(sessionId: sessionId) }
+        closeTerminal()
+    }
+
+    // MARK: - Split-view sidebar bridge (T-iPad-2)
+
+    /// Detail 面板当前显示的会话 → sidebar 选中态（二向绑定的 getter）。只反映
+    /// **adopted** 会话；未 adopted / 无打开的 detail → nil（占位「选择或新建
+    /// 会话」）。分栏与 stack 共享同一 `terminalController`（归 coordinator
+    /// 所有，与布局分支正交）。
+    var selectedSidebarItem: SidebarItem? {
+        terminalController?.terminalViewModel.sessionId.map(SidebarItem.session)
+    }
+
+    /// `NavigationSplitView` 的选中绑定。getter 反映 detail 会话；setter 复用
+    /// 既有路由（`open` / `presentProjects`）—— 分栏只是又一个触发面，绝不新开
+    /// 一条会话生命周期。取消选中（set nil）不主动关闭 detail。
+    var sidebarSelection: Binding<SidebarItem?> {
+        Binding(
+            get: { self.selectedSidebarItem },
+            set: { item in
+                guard let item else { return }
+                self.selectSidebarItem(item)
+            }
+        )
+    }
+
+    /// sidebar 触发面：把选中项映射到**同一** open(id) / open(nil) /
+    /// presentProjects API。切会话沿用单活 WS 不变式的 close→open（与
+    /// new-in-cwd / deep-link 切换同一套原语），`.projects` 走既有 sheet 呈现。
+    func selectSidebarItem(_ item: SidebarItem) {
+        switch item {
+        case .session(let sessionId):
+            switchTerminal(sessionId: sessionId)
+        case .newSession:
+            switchTerminal(sessionId: nil)
+        case .projects:
+            presentProjects()
+        }
+    }
+
+    /// 单活 WS 不变式下的会话切换：已在显示同一会话 → no-op（免无谓 churn）；
+    /// 否则先 `closeTerminal()`（旧会话记 last-seen 水位、engine detach）再
+    /// `open()`。复用既有原语，**非**平行生命周期。无 activeHost → no-op。
+    private func switchTerminal(sessionId: UUID?) {
+        guard let host = sessionList.activeHost else { return }
+        if let sessionId, selectedSidebarItem == .session(sessionId) { return }
+        if terminalController != nil { closeTerminal() }
+        open(SessionListViewModel.OpenRequest(id: UUID(), host: host, sessionId: sessionId))
+    }
+
     // MARK: - "在当前目录开新会话" (T-iOS-29)
 
     /// 当前终端会话的 cwd。解析次序：/live-sessions 行数据（server-adopted
@@ -235,3 +291,12 @@ final class AppCoordinator {
         PairingViewModel(store: environment.hostStore, probe: environment.probe)
     }
 }
+
+/// T-iPad-2 · split 模式下 sidebar 的选中项。与现有 `AppCoordinator` 路由
+/// 一一等价映射：`.session(id)` == `open(id)`、`.newSession` == `open(nil)`、
+/// `.projects` == `presentProjects()`。
+enum SidebarItem: Hashable {
+    case session(UUID)
+    case newSession
+    case projects
+}