feat: tmux 动态 resize（iPadOS 拖拽窗口/旋转自适应）

- ContentView 观测 onChange(geo.size)/onAppear → controller.containerResized
- containerResized: 点尺寸 × displayScale ÷ cell 像素 = 目标 cols×rows，去重 + debounce(200ms)
  → refresh-client -C WxH → tmux 重排回 %layout-change → 更新 pane frame
- cell 像素来自 raw 终端/pane surface metrics(InMemoryTerminalViewport.cellWidthPixels)；
  surface resize 回调只 noteCellPixels 不驱动 tmux（防反馈环，单向数据流）
- 验证：容器 1032x1280@2x cell16x35→129x73，tmux 根 rect 精确采纳，2 pane 复用不重建

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

apps/TerminalX/iOS/SSHTerminalModel.swift

@@ -124,12 +124,20 @@ final class TmuxByteChannel: @unchecked Sendable {
     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`）。
+/// 线程安全记录全屏终端格子数 + cell 像素尺寸（tmux attach/resize 时据此换算 `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() }
+    private var cols = 80, rows = 24, cellW = 0, cellH = 0
+    var value: (cols: Int, rows: Int, cellW: Int, cellH: Int) {
+        lock.lock(); defer { lock.unlock() }; return (cols, rows, cellW, cellH)
+    }
+    func set(cols: Int, rows: Int, cellW: Int, cellH: Int) {
+        lock.lock()
+        self.cols = max(1, cols); self.rows = max(1, rows)
+        if cellW > 0 { self.cellW = cellW }   // cell 尺寸稳定，保留最后有效值
+        if cellH > 0 { self.cellH = cellH }
+        lock.unlock()
+    }
 }
 
 /// M0 SSH 终端会话模型：SSHSession(libssh2) ⇄ GhosttyKit in-memory 终端，
@@ -188,7 +196,9 @@ 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
+                // 记录全屏格子 + cell 像素（tmux resize 换算用）。
+                grid.set(cols: Int(vp.columns), rows: Int(vp.rows),
+                         cellW: Int(vp.cellWidthPixels), cellH: Int(vp.cellHeightPixels))
                 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) }
             }
@@ -333,9 +343,10 @@ final class SSHTerminalModel: ObservableObject {
         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。
+        // 告知全屏格子数 + cell 像素 → attach 时 refresh-client -C、动态 resize 换算。
         let g = screenGrid.value
         controller.setClientSize(cols: g.cols, rows: g.rows)
+        controller.setCellPixels(w: g.cellW, h: g.cellH)
         tmuxController = controller
         if !initialBytes.isEmpty { controller.feed(Data(initialBytes)) }
     }