refactor: reorganize, add package (opencode, osgrep, beads), add ai agent shell

shells/jupyter-notebook.nix

@@ -0,0 +1,31 @@
+{ pkgs, python ? pkgs.python312, ... }:
+
+let
+  # Python environment with notebook tooling and core data-science libs
+  pythonWithNotebook = python.withPackages (ps:
+    with ps; [
+      altair
+      ipykernel
+      jupyterlab
+      matplotlib
+      numpy
+      pandas
+      polars
+      plotly
+      scipy
+      scikit-learn
+      seaborn
+    ]);
+in pkgs.mkShell {
+  name = "jupyter-notebook";
+  packages = [ pythonWithNotebook pkgs.ruff pkgs.pyright pkgs.git ];
+  shellHook = ''
+    export PYTHONNOUSERSITE=1
+    export JUPYTER_CONFIG_DIR="''${XDG_CONFIG_HOME:-$HOME/.config}/jupyter"
+    mkdir -p "$JUPYTER_CONFIG_DIR"
+    echo "Jupyter notebook shell ready"
+    echo "Python: ${python.version}"
+    echo "Launch notebook: jupyter lab"
+    echo "Launch classic: jupyter notebook"
+  '';
+}