Establish repository foundation and shared work environment

modules/capabilities/yookr-dev/environment.nix

@@ -0,0 +1,34 @@
+{
+  perSystem =
+    { pkgs, ... }:
+    let
+      tools = import ./_packages.nix { inherit pkgs; };
+    in
+    {
+      # Tooling only: no credential loading, mounts, or Python dependency installs.
+      devShells.workbench = pkgs.mkShell {
+        LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
+          pkgs.stdenv.cc.cc.lib
+          pkgs.zlib
+        ];
+        UV_PYTHON = "${pkgs.python314}/bin/python";
+        UV_PYTHON_DOWNLOADS = "never";
+        packages = [
+          tools.gardenctl
+          tools.gardenlogin
+        ]
+        ++ (with pkgs; [
+          k9s
+          kubectl
+          kubelogin-oidc
+          jq
+          just
+          python314
+          rclone
+          sops
+          util-linux
+          uv
+        ]);
+      };
+    };
+}