fix CI: exclude free-threaded Windows wheels; replace librosa with soundfile in tests

- Windows CIBW-BUILD patterns like "cp314*" also matched cp314t, so
  cibuildwheel additionally built a free-threaded wheel around the
  GIL-build dawdreamer.pyd (linked against python314.dll), which fails to
  import under python314t.dll. The regular cp314 wheel passed all 343
  tests in the same job. Use "cp31X-*" to build only the GIL variants.
- The macOS Intel test installs failed because librosa depends on numba
  and llvmlite, which no longer publish macosx x86_64 wheels. The tests
  only used librosa to load audio files, so load_audio_file now uses
  soundfile directly, with offset and duration slicing, resampling to the
  engine rate via scipy.signal.resample_poly, and float32 output. This
  drops the numba/llvmlite dependency on every platform.