Earlier quoted context omitted.
This is a good approach, though presumably the VM still has access to your Github credentials (via the browser) and your SSH keys? It'll limit the fallout of getting owned to anything reachable from Github (is it against Github's TOS to have multiple accounts?), less if you have 2FA (does there exist 2FA for SSH keys (I don't mean passphrases)?), but I think it would be better for just my build/run/test cycles to be…
It might be too cumbersome for most, and I might be more paranoid than average, but each project for me means a fresh VM, a new Keepass database and dedicated accounts. Then again I work mostly in ops, and I've seen first hand how badly things can go wrong so isolation and limiting blast radius takes precedence over daily convenience for me.
[0] https://www.qubes-os.org/doc/how-to-use-disposables/
[1] https://www.qubes-os.org/doc/how-to-copy-and-move-files/