Misc 1-1-2026

[matthewyang204]

Changes:

• Fix dependencies
• Use app-native Qt dialog rather than tk dialogs because this breaks macOS compatibility
  • Also improve it by adding support for file extensions
• Always save & load in UTF-8 or else it will break for non-ASCII files
• Make main.py a proper launcher rather than a duplicate to make it less messy
• Make file loading function more modular
  • Also fix the load/save functions not working at all
• Fix build system
• Handle both macOS app lifetime & ordinary Linux/Windows file open events
• Kill program if all tabs are closed (otherwise the program risks crashing due to out-of-range errors)

Please check that the changes work, but otherwise feel free to merge.