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/COPYING.iOS

@@ -0,0 +1,11 @@
+The Mosh developers are aware that the terms of service that apply to
+apps distributed via Apple's App Store services may conflict with
+rights granted under Mosh's license, the GNU General Public License,
+version 3. The Mosh copyright holders do not wish this conflict to
+prevent the otherwise-compliant distribution of Mosh-derived apps via
+the App Store. Therefore, we have committed not to pursue any license
+violation that results solely from the conflict between the GPLv3 and
+the Apple App Store terms of service. In other words, as long as you
+comply with the GPL in all other respects, including its requirements
+to provide users with source code and the text of the license, we will
+not object to your distribution of Mosh through the App Store.