feat: M3 mosh 挂起→恢复<3s（唤醒脉冲 + 会话状态机三相）

- SessionMachine 加 mosh 三相(moshActive/moshParked/moshResuming)+看门狗兜底，
  mosh 接管即拆 SSH、后台冻结不重建、前台唤醒脉冲等 SSP 续（+5 单测）
- bridge.go: Node.WakeUp()(tsnet InjectEvent+MagicSock.Rebind/ReSTUN) +
  MoshRelay.Rebind()(同端口重开 loopback、泵按 socket 生成容错)
- iosclient.cc: g_mosh_last_heard 探针(导出 mosh_last_heard_ms) + SIGCONT 全屏重绘
- MoshSession: nudge()(SIGCONT) + lastHeardMs()；SSHTerminalModel 前台脉冲三连
  + healthy 轮询 + beginBackgroundTask；URL scheme 供无头前台唤醒
- 验证(vohive-vm over tsnet)：15s 冻结→前台 wake pulse→1.3s recovered，<3s

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

packages/TXCore/Tests/TXCoreTests/SessionMachineTests.swift

@@ -125,4 +125,78 @@ struct SessionMachineTests {
         #expect(m2.reduce(.retryRequested) == [.startConnect])
         #expect(m2.phase == .connecting)
     }
+
+    // MARK: - M3 mosh 生命周期
+
+    private func connectedThenMosh() -> SessionMachine {
+        var m = SessionMachine()
+        _ = m.reduce(.connectRequested)
+        _ = m.reduce(.established)
+        return m
+    }
+
+    @Test("mosh 接管拆 SSH，之后忽略 transportClosed")
+    func moshTakeover() {
+        var m = connectedThenMosh()
+        let e = m.reduce(.moshEstablished)
+        #expect(m.phase == .moshActive)
+        #expect(e.contains(.teardownTransport))
+        // 底层 SSH 残连断开，不影响 mosh
+        #expect(m.reduce(.transportClosed(reason: "ssh eof")) == [])
+        #expect(m.phase == .moshActive)
+    }
+
+    @Test("mosh 后台→前台：唤醒脉冲 + 看门狗，收到 healthy 即恢复")
+    func moshSuspendResumeHealthy() {
+        var m = connectedThenMosh()
+        _ = m.reduce(.moshEstablished)
+        #expect(m.reduce(.enteredBackground) == [])
+        #expect(m.phase == .moshParked)
+        let e = m.reduce(.enteredForeground)
+        #expect(m.phase == .moshResuming(attempt: 1))
+        #expect(e.contains(.nudgeResume))
+        #expect(e.contains(.scheduleResumeWatchdog(ms: 3000)))
+        // SSP 续上
+        let e2 = m.reduce(.moshHealthy)
+        #expect(m.phase == .moshActive)
+        #expect(e2.contains(.cancelResumeWatchdog))
+    }
+
+    @Test("恢复看门狗：一次超时再脉冲，两次仍失败则兜底全量重建")
+    func moshResumeWatchdogFallback() {
+        var m = SessionMachine(resumeWatchdogMS: 3000, maxResumePulses: 2)
+        _ = m.reduce(.connectRequested)
+        _ = m.reduce(.established)
+        _ = m.reduce(.moshEstablished)
+        _ = m.reduce(.enteredBackground)
+        _ = m.reduce(.enteredForeground)          // moshResuming(1)
+        // 第一次看门狗到点 → 再脉冲，进 moshResuming(2)
+        let e1 = m.reduce(.resumeWatchdogFired)
+        #expect(m.phase == .moshResuming(attempt: 2))
+        #expect(e1.contains(.nudgeResume))
+        // 第二次看门狗到点 → 兜底全量重建
+        let e2 = m.reduce(.resumeWatchdogFired)
+        #expect(m.phase == .reconnecting(attempt: 1))
+        #expect(e2.contains(.teardownMosh))
+        #expect(e2.contains(.startConnect))
+    }
+
+    @Test("mosh 主循环退出转 failed 并拆除")
+    func moshExited() {
+        var m = connectedThenMosh()
+        _ = m.reduce(.moshEstablished)
+        let e = m.reduce(.moshExited(rc: 1))
+        if case .failed = m.phase {} else { Issue.record("期望 failed，实际 \(m.phase)") }
+        #expect(e.contains(.teardownMosh))
+    }
+
+    @Test("mosh 恢复中进后台取消看门狗")
+    func moshResumingToBackground() {
+        var m = connectedThenMosh()
+        _ = m.reduce(.moshEstablished)
+        _ = m.reduce(.enteredBackground)
+        _ = m.reduce(.enteredForeground)          // moshResuming(1)
+        #expect(m.reduce(.enteredBackground) == [.cancelResumeWatchdog])
+        #expect(m.phase == .moshParked)
+    }
 }