StemSplit Studio 0.1.1

Fixes two problems in 0.1.0.

• M4A/AAC was listed as a supported format but the audio library cannot decode it, so picking an M4A file failed. It is no longer offered, and if one is passed in anyway the app now says to convert it to MP3, WAV or FLAC.
• When the engine reported a problem, a second generic message overwrote it, so failures showed only 'stopped unexpectedly (code 1)'. Real error messages now reach the user.

Supported input: MP3, WAV, FLAC, OGG, AIFF.
Windows 10 and 11, 64-bit.