* feat!: replace zellij with tuios and switch to ghostty + kitty
Terminal environment overhaul:
- add the tuios flake input (upstream 0.8.5; nixpkgs has 0.8.1) and link
the checked-in config out-of-store; auto-start tuios in nushell instead
of zellij
- remove zellij entirely: both modules, config, README and nushell
completions
- remove foot and alacritty, which lack the Kitty graphics protocol;