feat: tmux 多 pane 分屏（pane-per-surface + refresh-client -C 尺寸协调）

- TmuxController 重构为 pane-per-surface：TmuxPaneSurface(session+state+gate/pane)
  + TmuxWindow(panes 字典/visibleLayout 渲染/fullLayout diff) + surfaceByPane O(1) 路由
- 尺寸走路线 b：attach 发 refresh-client -C WxH 让 tmux 布局，pane surface 尺寸取 layout
  rect（%output 按 tmux pane 宽高排版，一致才不换行/清屏错乱）；surface resize 只断言不反向驱动
- applyLayout reconcile(增删留、复用不重建)；新 pane capture-pane %end 前丢弃 %output
- 输入绑 pane→send-keys -t %self；tap→select-pane；ContentView 按 rect 绝对定位分屏 + 焦点边框
- 前置修复：tmux 网关字节改 TmuxByteChannel(AsyncStream 单消费者)保序，防多 pane 打碎协议
- 验证(192.168.9.199 直连 tmux -CC attach)：左右 pane 各渲染 LEFT/RIGHT 输出、实时、无错乱

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/TerminalX/iOS/SSHTerminalModel.swift

@@ -111,6 +111,27 @@ final class OutputGate: @unchecked Sendable {
     }
 }
 
+/// tmux 网关字节的有序事件（enter 携初始字节 / bytes 后续）。经单一 AsyncStream 传到主线程，
+/// 杜绝"每 chunk 起独立 Task"导致的乱序（多 pane 高吞吐会打碎 % 协议解析）。
+enum TmuxByteEvent: Sendable { case enter([UInt8]); case bytes([UInt8]) }
+
+/// 线程安全承载 tmux 字节通道的 continuation（传输后台线程 yield，主线程单消费者取用）。
+final class TmuxByteChannel: @unchecked Sendable {
+    let stream: AsyncStream<TmuxByteEvent>
+    private let cont: AsyncStream<TmuxByteEvent>.Continuation
+    init() { (stream, cont) = AsyncStream.makeStream() }
+    func enter(_ b: [UInt8]) { cont.yield(.enter(b)) }
+    func bytes(_ b: [UInt8]) { cont.yield(.bytes(b)) }
+}
+
+/// 线程安全记录全屏终端格子数（tmux attach 时据此 `refresh-client -C`）。
+final class GridBox: @unchecked Sendable {
+    private let lock = NSLock()
+    private var v: (cols: Int, rows: Int) = (80, 24)
+    var value: (cols: Int, rows: Int) { lock.lock(); defer { lock.unlock() }; return v }
+    func set(cols: Int, rows: Int) { lock.lock(); v = (max(1, cols), max(1, rows)); lock.unlock() }
+}
+
 /// M0 SSH 终端会话模型：SSHSession(libssh2) ⇄ GhosttyKit in-memory 终端，
 /// 由 TXCore.SessionMachine 编排生命周期（断线指数退避自动重连、后台冻结/前台恢复）。
 @MainActor
@@ -152,9 +173,14 @@ final class SSHTerminalModel: ObservableObject {
     private var bgTask: UIBackgroundTaskIdentifier = .invalid
     #endif
 
+    private let tmuxChannel = TmuxByteChannel()
+    /// 全屏终端格子数（raw 模式 surface resize 时记录；tmux attach 用于 refresh-client -C）。
+    let screenGrid = GridBox()
+
     init() {
         let holder = TransportHolder()
         let moshHolder = MoshHolder()
+        let grid = screenGrid
         let session = InMemoryTerminalSession(
             // 输入/resize：mosh 激活时路由到 mosh，否则走 SSH transport。
             write: { data in
@@ -162,6 +188,7 @@ final class SSHTerminalModel: ObservableObject {
                 else { holder.transport?.send(data) }
             },
             resize: { vp in
+                grid.set(cols: Int(vp.columns), rows: Int(vp.rows))   // 记录全屏格子供 tmux
                 if let m = moshHolder.session { m.resize(cols: Int(vp.columns), rows: Int(vp.rows)) }
                 else { holder.transport?.resize(cols: vp.columns, rows: vp.rows) }
             }
@@ -173,6 +200,18 @@ final class SSHTerminalModel: ObservableObject {
         self.session = session
         self.state = state
         self.gate = OutputGate(session: session)
+
+        // tmux 网关字节：单消费者按序处理（enter 建 controller+喂初始，bytes 续喂）。
+        let ch = tmuxChannel
+        Task { @MainActor [weak self] in
+            for await ev in ch.stream {
+                guard let self else { continue }
+                switch ev {
+                case .enter(let initial): self.enterTmux(initialBytes: initial)
+                case .bytes(let b): self.tmuxController?.feed(Data(b))
+                }
+            }
+        }
     }
 
     // MARK: - 公开入口
@@ -285,18 +324,18 @@ final class SSHTerminalModel: ObservableObject {
 
     private lazy var tmuxRouter = TmuxRouter(
         rawGate: gate,
-        enterGateway: { [weak self] after in
-            Task { @MainActor in self?.enterTmux(initialBytes: after) }
-        },
-        gatewayBytes: { [weak self] bytes in
-            Task { @MainActor in self?.tmuxController?.feed(Data(bytes)) }
-        }
+        // 经有序通道传主线程（enter 先于后续 bytes，单消费者保序）。
+        enterGateway: { [tmuxChannel] after in tmuxChannel.enter(after) },
+        gatewayBytes: { [tmuxChannel] bytes in tmuxChannel.bytes(bytes) }
     )
 
     private func enterTmux(initialBytes: [UInt8]) {
         let holder = self.holder
         let controller = TmuxController(sendRaw: { data in holder.transport?.send(data) })
         controller.onExit = { [weak self] in Task { @MainActor in self?.exitTmux() } }
+        // 告知全屏格子数 → attach 时 refresh-client -C，让 tmux 按此尺寸布局。
+        let g = screenGrid.value
+        controller.setClientSize(cols: g.cols, rows: g.rows)
         tmuxController = controller
         if !initialBytes.isEmpty { controller.feed(Data(initialBytes)) }
     }