C# test suite and C reproducer validating DLL initialization.
The probe test (DllMainWorkaround_IsStillActive) checks that the CRT
workaround is compiled in via ghostty_crt_workaround_active(). When
Zig fixes MSVC DLL CRT init, removing the DllMain will make this test
fail with instructions on how to verify the fix and clean up.
ghostty_init is tested via the C reproducer (test_dll_init.c) rather
than C# because the global state teardown crashes the test host on
DLL unload. The C reproducer exits without FreeLibrary.
