Moving nvim plugins to Nix breaks git-clone users

When a published Neovim config (also a subtree in a NixOS repo) switches from vim.pack/lazy.nvim to nixpkgs vimPlugins, the plain git clone ~/.config/nvim && nvim install silently stops working: nothing downloads plugins anymore, so the first require (e.g. hotpot) fails. Check the README install path and decide Nix-only or keep a fallback before migrating. A fallback that keeps one list: store plugins as JSON {url, nixpkgs attr}, read with builtins.fromJSON in Nix, and in init.lua call vim.pack.add with the URLs only when the bootstrap plugin is not already on the packpath.