i18n: test_lock() and lang_test_lock() used to be TWO different static
mutexes, so the i18n tests and the ~30 app/actions/dialogs tests that
mutate the language global never excluded each other. Windows thread
scheduling exposed the race: tr_falls_back_to_english_then_the_key got
the English value because another test flipped the language mid-assert.
Both entry points now lock the same mutex.
oak_test_plugin.c: on Windows the plugin DLL has its own CRT
environment block, so getenv() never sees what the host's
std::env::set_var set via SetEnvironmentVariableW — the interact
lifecycle test's marker file stayed empty ("lifecycle actions
missing: []"). Read the marker path through GetEnvironmentVariableA
on _WIN32.
Mike-Solar
3efdee5a10