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/conformance/defs.bzl

@@ -0,0 +1,28 @@
+# PLEASE DO NOT DEPEND ON THE CONTENTS OF THIS FILE, IT IS UNSTABLE.
+
+def conformance_test(name, testee, failure_list = None, text_format_failure_list = None):
+    args = ["--testee %s" % _strip_bazel(testee)]
+    failure_lists = []
+    if failure_list:
+        args = args + ["--failure_list %s" % _strip_bazel(failure_list)]
+        failure_lists = failure_lists + [failure_list]
+    if text_format_failure_list:
+        args = args + ["--text_format_failure_list %s" % _strip_bazel(text_format_failure_list)]
+        failure_lists = failure_lists + [text_format_failure_list]
+
+    native.sh_test(
+        name = name,
+        srcs = ["//conformance:conformance_test_runner.sh"],
+        data = [testee] + failure_lists + [
+            "//conformance:conformance_test_runner",
+        ],
+        args = args,
+        deps = [
+            "@bazel_tools//tools/bash/runfiles",
+        ],
+    )
+
+def _strip_bazel(testee):
+    if testee.startswith("//"):
+        testee = testee.replace("//", "com_google_protobuf/")
+    return testee.replace(":", "/")