[freakboy3742]

Clean up some unused imports and variables to ensure that generated projects pass a default Ruff configuration.

• The ROW and COLUMN imports were unused in the default Toga configuration (but can be easily added when needed)
• The main_window object was never used in the PySide6 configuration.

Refs beeware/.github#380.

PR Checklist:

• I will abide by the BeeWare Code of Conduct
• I have read and have followed the CONTRIBUTING.md file
• This PR was generated or assisted using an AI tool

[mhsmith]

Is it necessary to assign this to a variable to keep it in existence? Doesn't showing the window automatically add a reference from the app?

If it is necessary, I think a normal variable name and a noqa comment with an explanation would be better than relying on _ for something so important.

[freakboy3742]

It has to be assigned to something - otherwise the object passes out of scope and is garbage collected, so the window is never displayed.

I'd rather avoid a noqa in freshly generated template code; I've found another solution - factor the show() out of init_ui so that main_window is used. It's arguably a better idea to keep displaying the window indpendent of construction anyway, so we can kill 2 birds with 1 stone.