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/protobuf/cmake/protobuf-lite.pc.cmake

@@ -0,0 +1,11 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=@CMAKE_INSTALL_PREFIX@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: Protocol Buffers
+Description: Google's Data Interchange Format
+Version: @protobuf_VERSION@
+Libs: -L${libdir} -lprotobuf-lite @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir}
+Conflicts: protobuf