Vondri/gmailchecker ? reverse-engineered prompt

Build me a simple Python script that checks Gmail usernames and tells me which ones look valid and which ones don’t.

I want it to work from the command line with a help screen, be able to check one email at a time or a whole text file of usernames, and support a quiet mode that skips the banner. It should also let me save the valid results and invalid results into separate files, and set a delay between checks so it does not run too fast.

Make it easy to run on Windows and Linux, with clear usage examples. If you need to look up current docs online for anything small, feel free to do that. Keep it lightweight and straightforward, like a small utility script someone can just run with a few flags.