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/TerminalContainerView.swift

@@ -22,6 +22,10 @@ struct TerminalContainerView: View {
     /// T-iOS-29 · pass-through to TerminalScreen's toolbar/exit-banner
     /// "在当前目录开新会话" action (RootView supplies the coordinator hop).
     var onNewSessionInCwd: (@MainActor () -> Void)? = nil
+    /// T-iPad-3 · pass-through to TerminalScreen's pointer context-menu
+    /// "结束会话" action (root layers supply the coordinator hop). nil on
+    /// surfaces without a kill affordance (e.g. previews).
+    var onKillSession: (@MainActor () -> Void)? = nil
     /// Epoch of a plan gate the user swiped away — suppresses re-present for
     /// THAT gate only; a new epoch re-presents automatically.
     @State private var dismissedPlanGateEpoch: Int?
@@ -48,7 +52,8 @@ struct TerminalContainerView: View {
     var body: some View {
         TerminalScreen(
             viewModel: controller.terminalViewModel,
-            onNewSessionInCwd: onNewSessionInCwd
+            onNewSessionInCwd: onNewSessionInCwd,
+            onKillSession: onKillSession
         )
         .id(controller.generation)
             .navigationBarTitleDisplayMode(.inline)