test(windows): build and run the test suite for Windows from WSL

scripts/test-windows.sh cross-compiles ObsidianDragonTests.exe (and the
fake_dragonxd stub) with mingw into build/windows-tests, reusing the
toolchain and dependency sources from build/windows, and runs it from
WSL through Windows interop (or wine). All tests pass on Windows.

CMake:
- Windows forced BUILD_TESTING OFF in the cache to keep curl's tests
  out, which also removed ObsidianDragonTests from every Windows build.
  Hide it from curl with a scoped variable instead, and restore our
  cache value afterwards (curl's cmake_dependent_option FORCE-writes
  it). Windows still defaults to OFF, so release builds are unchanged.
- ObsidianDragonTests now depends on copy_langs: i18n.cpp includes the
  generated embedded/lang_*.h, so a tree that builds only the tests
  failed (latent on Linux too).
- Link the Windows system libraries the tests need.

Tests:
- testTmpPath/fixtureDir/removeTree helpers: no hard-coded /tmp, a
  runtime fixture-dir override (the compiled-in path is a Linux one),
  and best-effort cleanup that can't abort the suite.
- Close the explorer cache before deleting its directory (Windows
  can't delete an open file).
- Compile out the address-book and wallet-index round-trips on Windows:
  getConfigDir() uses SHGetFolderPath there, which no environment
  variable redirects, so they would overwrite the real
  %APPDATA%\ObsidianDragon files.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CMakeLists.txt

@@ -155,6 +155,11 @@ if(DRAGONX_ENABLE_LITE_BACKEND)
     set(DRAGONX_LITE_BACKEND_READY ON)
 endif()
 
+# Windows (mingw cross) builds skip the large test target unless asked for with -DBUILD_TESTING=ON
+# (scripts/test-windows.sh does that in its own build/windows-tests tree), so release builds are unchanged.
+if(WIN32 AND NOT DEFINED BUILD_TESTING)
+    set(BUILD_TESTING OFF CACHE BOOL "Build the testing tree.")
+endif()
 include(CTest)
 
 # Output directories
@@ -266,7 +271,11 @@ if(WIN32)
     set(BUILD_CURL_EXE OFF CACHE BOOL "" FORCE)
     set(BUILD_SHARED_LIBS OFF CACHE BOOL "" FORCE)
     set(CURL_STATICLIB ON CACHE BOOL "" FORCE)
-    set(BUILD_TESTING OFF CACHE BOOL "" FORCE)
+    # Keep curl's own tests out, without switching off ObsidianDragonTests for every Windows build:
+    # hide BUILD_TESTING behind a normal variable while curl configures, then restore our cache value
+    # (curl's cmake_dependent_option(BUILD_TESTING ...) FORCE-writes the OFF it saw into the cache).
+    set(_dragonx_build_testing "${BUILD_TESTING}")
+    set(BUILD_TESTING OFF)
     set(CURL_DISABLE_LDAP ON CACHE BOOL "" FORCE)
     set(CURL_DISABLE_LDAPS ON CACHE BOOL "" FORCE)
     set(CURL_USE_SCHANNEL ON CACHE BOOL "" FORCE)  # Use Windows native SSL
@@ -275,6 +284,8 @@ if(WIN32)
     set(CURL_ZLIB OFF CACHE BOOL "" FORCE)
     set(HTTP_ONLY ON CACHE BOOL "" FORCE)
     FetchContent_MakeAvailable(curl)
+    unset(BUILD_TESTING)
+    set(BUILD_TESTING "${_dragonx_build_testing}" CACHE BOOL "Build the testing tree." FORCE)
     set(CURL_LIBRARIES libcurl_static)
     set(CURL_INCLUDE_DIRS ${curl_SOURCE_DIR}/include ${curl_BINARY_DIR}/lib/curl)
 else()
@@ -1233,6 +1244,13 @@ if(BUILD_TESTING)
     if(UNIX)
         target_link_libraries(ObsidianDragonTests PRIVATE ${CMAKE_DL_LIBS})
     endif()
+    if(WIN32)
+        target_link_libraries(ObsidianDragonTests PRIVATE ws2_32 crypt32 wldap32 psapi iphlpapi shell32 ole32 advapi32 bcrypt)
+    endif()
+    # i18n.cpp includes the generated embedded/lang_*.h headers; a tree that builds only this target needs them too.
+    if(TARGET copy_langs)
+        add_dependencies(ObsidianDragonTests copy_langs)
+    endif()
 
     add_test(NAME ObsidianDragonPhase4Tests COMMAND ObsidianDragonTests)
 endif()