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/scripts/wrap-compiler-for-flag-check

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+# There is no way to make clang's "argument unused" warning fatal.  So when
+# configure checks for supported flags, it runs $CC, $CXX, $LD via this
+# wrapper.
+#
+# Ideally the search string would also include 'clang: ' but this output might
+# depend on clang's argv[0].
+
+if out=`"$@" 2>&1`; then
+  echo "$out"
+  if echo "$out" | grep 'warning: argument unused' >/dev/null; then
+    echo "$0: found clang warning"
+    exit 1
+  else
+    exit 0
+  fi
+else
+  code=$?
+  echo "$out"
+  exit $code
+fi