feat: 完成 M2 mosh（LAN + tsnet 端到端验证）

- mosh(blinksh/ios C++)+protobuf-lite 交叉编译为 MoshCore.xcframework
  （CommonCrypto 后端、含 arm64 模拟器 slice；绕 autotools 用 CMake 直编 + 手写 config.h）
- tsnet 桥新增 UDP relay（StartMoshRelay：loopback↔tsnet.Dial 逐包搬运）
- MoshSession（pipe↔FILE*/pthread/SIGWINCH）+ MoshConnectScanner（TXCore，+4 单测=39）
- SSHTerminalModel 编排：SSH 引导 mosh-server→解析 MOSH CONNECT→relay→mosh 接管
- LAN 直连 + mosh-over-tsnet 均端到端验证通过，R1(tsnet UDP 数据报语义) 证伪

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

vendor/mosh/debian/control

@@ -0,0 +1,21 @@
+Source: mosh
+Section: net
+Priority: optional
+Maintainer: Keith Winstein <keithw@mit.edu>
+Build-Depends: debhelper (>= 7.0.50), autotools-dev, protobuf-compiler, libprotobuf-dev, dh-autoreconf, pkg-config, libutempter-dev, zlib1g-dev, libncurses5-dev, libssl-dev, bash-completion
+Standards-Version: 3.9.6.1
+Homepage: http://mosh.mit.edu
+Vcs-Git: git://github.com/keithw/mosh.git
+Vcs-Browser: https://github.com/keithw/mosh
+
+Package: mosh
+Architecture: any
+Pre-Depends: dpkg (>= 1.15.7.2)
+Depends: ${shlibs:Depends}, ${misc:Depends}, openssh-client
+Recommends: libio-socket-ip-perl
+Description: Mobile shell that supports roaming and intelligent local echo
+ Mosh is a remote terminal application that supports:
+   - intermittent network connectivity,
+   - roaming to different IP address without dropping the connection, and
+   - intelligent local echo and line editing to reduce the effects
+     of "network lag" on high-latency connections.