fix: move vendoring of nixpkgs and select into root devshell

devShell.nix

@@ -1,4 +1,4 @@
-{ ... }:
+{ inputs, ... }:
 {
   perSystem =
     {
@@ -39,6 +39,10 @@
         shellHook = ''
           echo -e "${ansiEscapes.green}switch to another dev-shell using: select-shell${ansiEscapes.reset}"
           export PRJ_ROOT=$(git rev-parse --show-toplevel)
+
+          # vendoring / needed for impure tests
+          ln -sfT ${self'.packages.clan-cli.nixpkgs} "$PRJ_ROOT/pkgs/clan-cli/clan_cli/nixpkgs"
+          ln -sfT ${inputs.nix-select} "$PRJ_ROOT/pkgs/clan-cli/clan_cli/select"
         '';
       };
     };