初始提交：terminalX 可运行态（M0/M1/M1.5 已真机验证）

- M0: libghostty SSH 终端（渲染/输入/连接）+ 白屏修复(OutputGate) + 会话状态机/自动重连
- M1: tsnet 用户态组网 + SSH-over-tsnet(fd 桥)，shell 级真机验证；R5(Go+gvisor+C+++Swift 同进程) retire
- M1.5: tmux -CC 原生 tab（MVP）
- 结构: packages/(TXCore·TXTransport), apps/TerminalX, vendor/(libghostty-spm/libssh2/mbedtls/tsnet-bridge), artifacts/
- 文档: CLAUDE.md + docs/HANDOFF.md（新会话入口）
- 环境: 认证代理→依赖 vendor 本地化；Go 在 ~/.local/go；仅模拟器/未签名
- 待续: M2 mosh, tmux 多 pane, M4 安全(host key/SE)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vendor/libssh2/cmake/CheckFunctionExistsMayNeedLibrary.cmake

@@ -0,0 +1,81 @@
+# Copyright (C) Alexander Lamaison <alexander.lamaison@gmail.com>
+#
+# Redistribution and use in source and binary forms,
+# with or without modification, are permitted provided
+# that the following conditions are met:
+#
+#   Redistributions of source code must retain the above
+#   copyright notice, this list of conditions and the
+#   following disclaimer.
+#
+#   Redistributions in binary form must reproduce the above
+#   copyright notice, this list of conditions and the following
+#   disclaimer in the documentation and/or other materials
+#   provided with the distribution.
+#
+#   Neither the name of the copyright holder nor the names
+#   of any other contributors may be used to endorse or
+#   promote products derived from this software without
+#   specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+# CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+# OF SUCH DAMAGE.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+
+# - check_function_exists_maybe_need_library(<function> <var> [lib1 ... libn])
+#
+# Check if function is available for linking, first without extra libraries, and
+# then, if not found that way, linking in each optional library as well.  This
+# function is similar to autotools AC_SEARCH_LIBS.
+#
+# If the function if found, this will define <var>.
+#
+# If the function was only found by linking in an additional library, this
+# will define NEED_LIB_LIBX, where LIBX is the one of lib1 to libn that
+# makes the function available, in uppercase.
+#
+# The following variables may be set before calling this macro to
+# modify the way the check is run:
+#
+#  CMAKE_REQUIRED_FLAGS = string of compile command line flags
+#  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
+#  CMAKE_REQUIRED_INCLUDES = list of include directories
+#  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
+#
+
+include(CheckFunctionExists)
+include(CheckLibraryExists)
+
+function(check_function_exists_may_need_library _function _variable)
+
+  check_function_exists(${_function} ${_variable})
+
+  if(NOT ${_variable})
+    foreach(_lib IN LISTS ARGN)
+      string(TOUPPER ${_lib} _up_lib)
+      # Use new variable to prevent cache from previous step shortcircuiting
+      # new test
+      check_library_exists(${_lib} ${_function} "" HAVE_${_function}_IN_${_lib})
+      if(HAVE_${_function}_IN_${_lib})
+        set(${_variable} 1 CACHE INTERNAL "Function ${_function} found in library ${_lib}")
+        set(NEED_LIB_${_up_lib} 1 CACHE INTERNAL "Need to link ${_lib}")
+        break()
+      endif()
+    endforeach()
+  endif()
+
+endfunction()