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/.travis.yml

@@ -0,0 +1,33 @@
+os:
+  - linux
+  - osx
+
+cache:
+  - apt
+
+language: cpp
+sudo: required
+dist: trusty
+
+addons:
+  apt:
+    packages:
+    - protobuf-compiler
+    - libprotobuf-dev
+    - libutempter-dev
+    - tmux			# test suite
+    - perl			# test suite
+
+before_install:
+  - if test "$TRAVIS_OS_NAME" = osx; then brew update; fi
+  - if test "$TRAVIS_OS_NAME" = osx; then brew install protobuf tmux; fi
+  - if test "$TRAVIS_OS_NAME" = osx; then brew outdated protobuf tmux || brew upgrade protobuf tmux; fi
+  - git fetch --tags --unshallow
+
+script:
+  - ./autogen.sh
+  - ./configure --enable-compile-warnings=error --enable-examples
+  - AM_TESTS_REDIRECT='9>&2' make distcheck 9>&2
+
+notifications:
+  irc: "chat.freenode.net#mosh"