fix(vim): replace unavailable peaksea colorscheme with catppuccin-mocha

peaksea is neither in the plugin list nor packaged in nixpkgs vimPlugins,
so `colorscheme peaksea` errored on startup and vim fell back to the
default scheme. Add catppuccin-vim and select catppuccin_mocha (matching
the swaylock/dunst palette); drop the dead peaksea packadd guard.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lyrathorpe/home/editor.nix

@@ -9,6 +9,7 @@
       ale
       vim-fugitive
       vim-indent-guides
+      catppuccin-vim
     ];
     settings = {
       expandtab = false;
@@ -17,13 +18,10 @@
     };
     extraConfig = ''
       let g:indent_guides_enable_on_vim_startup = 1
-      if v:version < 802
-        packadd! peaksea
-      endif
       syntax enable
-      colorscheme peaksea
       set termguicolors
       set background=dark
+      colorscheme catppuccin_mocha
       au BufNewFile,BufRead *Jenkinsfile setf groovy
     '';
   };