feat: nix flake, uv2nix build, dev shell and home manager

nix/python.nix

@@ -0,0 +1,28 @@
+# nix/python.nix — uv2nix virtual environment builder
+{
+  python311,
+  lib,
+  callPackage,
+  uv2nix,
+  pyproject-nix,
+  pyproject-build-systems,
+}:
+let
+  workspace = uv2nix.lib.workspace.loadWorkspace { workspaceRoot = ./..; };
+
+  overlay = workspace.mkPyprojectOverlay {
+    sourcePreference = "wheel";
+  };
+
+  pythonSet =
+    (callPackage pyproject-nix.build.packages {
+      python = python311;
+    }).overrideScope
+      (lib.composeManyExtensions [
+        pyproject-build-systems.overlays.default
+        overlay
+      ]);
+in
+pythonSet.mkVirtualEnv "hermes-agent-env" {
+  hermes-agent = [ "all" ];
+}