fix: Restore to project directory after using nodewhisper

[yannagrebah]

This PR fixes a minor oversight. When using nodewhisper(), it changes the current working directory to ./cpp/whisper.cpp instead of the project directory. This could cause problems when using other processes that rely on the current working directory.
This just restores the current directory to the project directory after all functions are done. Funny enough, this was already handled when an error occurred with handleError().

[Sleavely]

Could you apply the same finally-statement in src/autoDownloadModel.ts? It also only resets in the catch-block.

Edit: And in src/downloadModel.ts which doesn't seem to have any cleanup logic at all.