Switching nvim colorschemes leaves hardcoded hex and Gruvbox* groups behind

When moving a Neovim config from gruvbox to catppuccin, the colorscheme switch alone is not enough. Plugin setups often hardcode gruvbox hex values (bufferline highlights, lualine separator groups) or link to gruvbox-only groups like GruvboxOrange/GruvboxFg0 (e.g. a snacks dashboard), and those stay brown or go unstyled. Grep the config for '#[0-9a-f]{6}' and 'Gruvbox' and branch on vim.g.colors_name, which is set by the time later modules load if the colorscheme is required first. On the catppuccin branch, take colors from require('catppuccin.palettes').get_palette(flavour), or link to generic groups such as Comment or @constant.builtin. That keeps the old theme selectable with a one-line colorscheme change.