How can I set up the WP-CLI development environment for my own purpose/use?

[femboymcfox]

How can I set up the WP-CLI development environment step by step?

I'm trying to make my own changes to the word press core and wp-cli command line, for an example, I wanted to rename the folder "admin" throughout the word press core and environment but I'd need to compile my own wp-cli command line, just for fun and my own private use as I'm trying to learn new things but I'm having trouble setting up wp-cli-dev enviroment, like getting an error thrown like "The url supplied for the path (wp-cli.github.com) repository does not exist",
I'm not sure if it's just the help/readme guide is up to date or if I am doing something wrong, if anyone could help me that would be wonderful! and I know there's other and better ways I could do this but, I wanna do it by modifying the core itself. Not by using plugins or anything else. I would like to have my own whole complete development environment setup that WordPress developers have. I'd also like to compile my own modified .phar file. I also tried to clone all the packages from wp-cli to wp-cli-dev but I seem to have problems with that as it asks me for login information?
(I fixed this by running a command that just cloned all active repos, if you want I can put it down below)

EDIT:

I managed to fix all the issues above, I generated the .phar file but I only did it through php. Could I do it the same way it's setup as in through GitHub workflows? I would love to learn a bit more about how all of this works and what all the packages do that I cloned in wp-cli-dev. Like when I generated the .phar file, what does that build exactly? Let's say i want to make future changes to other packages in the wp-cli-dev, wp-cli projects, do I have to separately build and compile them or is that all compiled and bundled in the .phar?
What else could I learn about that's useful for the WordPress core, WP-CLI and other projects that's being used in WordPress? I apologize if these sound like really stupid questions, I'm not good with vocabulary and I'm also young and new to development especially php, html, css and anything website related. I would love to plan on being a future contributor to the wordpress and wp-cli project but I wanna learn more. Thanks so much for reading, I would appreciate any information that's helpful!