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/WebTermTests/LayoutPolicyTests.swift

@@ -0,0 +1,28 @@
+import SwiftUI
+import Testing
+@testable import WebTerm
+
+/// T-iPad-2 · 自适应根视图的唯一 size-class 决策点（仿 `PrivacyShadePolicy`
+/// 的纯谓词先例）。regular 宽度 → 分栏（sidebar+detail）；compact/未知 →
+/// 现有 iPhone stack 路径。这是**唯一**判据 —— 视图里严禁散落
+/// `if sizeClass == …`（PLAN_IOS_IPAD §4）。
+///
+/// 覆盖 `UserInterfaceSizeClass` 的三种可能取值（.regular / .compact / nil），
+/// 后者是「size class 尚未确定」的最保守回退：退到现有已测路径。
+@Suite("LayoutPolicy (T-iPad-2)")
+struct LayoutPolicyTests {
+    @Test("regular 宽度 → split（iPad 全屏/大分屏：sidebar + detail）")
+    func regularIsSplit() {
+        #expect(LayoutPolicy.mode(horizontalSizeClass: .regular) == .split)
+    }
+
+    @Test("compact 宽度 → stack（iPhone / iPad Slide Over：字节级复用现有路径）")
+    func compactIsStack() {
+        #expect(LayoutPolicy.mode(horizontalSizeClass: .compact) == .stack)
+    }
+
+    @Test("nil（size class 未定）→ stack（最保守：退现有 iPhone 路径）")
+    func nilIsStack() {
+        #expect(LayoutPolicy.mode(horizontalSizeClass: nil) == .stack)
+    }
+}