feat: add claude-code package

- Add Nix package for @anthropic-ai/claude-code (v2.1.59)
- Add package-lock.json with optional dependencies for all platforms
- Include update script for automated version updates
- Add module integration with custom package reference
- Rename claude shell alias to claude-custom

Refs: https://github.com/anthropics/claude-code

packages/claude-code/update.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env nix-shell
+#!nix-shell --pure --keep NIX_PATH -i bash --packages nodejs nix-update git cacert
+
+set -euo pipefail
+
+version=$(npm view @anthropic-ai/claude-code version)
+
+# Update version and hashes
+AUTHORIZED=1 NIXPKGS_ALLOW_UNFREE=1 nix-update claude-code --version="$version" --generate-lockfile
+nix-update vscode-extensions.anthropic.claude-code --use-update-script --version "$version"