feat: generate terminal extras for all palette variants

[marekh19]

Resolves #6

Terminal/shell extras now cover every palette variant, not just night.

• Each generator (ghostty, kitty, alacritty, wezterm, tmux, fish, fzf) runs once per style.
• Night stays canonical default (unsuffixed); moon/dawn get a -<variant> filename suffix.
• WezTerm scheme name tracks the variant so the three files don't collide on meowsoot.
• README documents the suffixed files and states night is the default.