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/KeyBarVisibilityTests.swift

@@ -0,0 +1,33 @@
+import Testing
+@testable import WebTerm
+
+/// T-iPad-3 · KeyBar 可见性纯谓词。硬件键盘在场时软键盘 KeyBar
+/// （`inputAccessoryView`）冗余 → 默认隐；无硬件键盘 → 显（iPhone 行为不变）；
+/// 用户显式切换（`userOverride`）始终压过自动默认。硬件态经参数注入（模拟器
+/// 硬件键盘状态未必可脚本化 —— 谓词单测是真值源）。
+@Suite("KeyBarVisibility (T-iPad-3)")
+struct KeyBarVisibilityTests {
+    // MARK: - 自动默认（跟随硬件键盘在场）
+
+    @Test("硬件键盘在场 + 无用户覆盖 → 隐藏（软 KeyBar 冗余）")
+    func hardwarePresentAutoHides() {
+        #expect(KeyBarVisibility.isVisible(hardwareKeyboardPresent: true, userOverride: nil) == false)
+    }
+
+    @Test("无硬件键盘 + 无用户覆盖 → 显示（iPhone 默认，零回归）")
+    func noHardwareAutoShows() {
+        #expect(KeyBarVisibility.isVisible(hardwareKeyboardPresent: false, userOverride: nil) == true)
+    }
+
+    // MARK: - 用户覆盖压过自动
+
+    @Test("用户强制显示压过硬件在场的自动隐藏")
+    func userForceShowWinsOverHardware() {
+        #expect(KeyBarVisibility.isVisible(hardwareKeyboardPresent: true, userOverride: true) == true)
+    }
+
+    @Test("用户强制隐藏压过无硬件的自动显示")
+    func userForceHideWinsOverNoHardware() {
+        #expect(KeyBarVisibility.isVisible(hardwareKeyboardPresent: false, userOverride: false) == false)
+    }
+}