nixvim: replace telescope with snacks.nvim picker

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

modules/home/nixvim/plugins/editor/snacks.nix

@@ -0,0 +1,8 @@
+{ pkgs, ... }: {
+  programs.nixvim = {
+    extraPlugins = [ pkgs.vimPlugins.snacks-nvim ];
+    extraConfigLua = ''
+      require("snacks").setup({ picker = { enabled = true } })
+    '';
+  };
+}