feat(nix): add flake with auto-versioned Node.js and pnpm

- Add Nix flake for development environment
- Auto-detect Node.js and pnpm versions from package.json
- Configure development tools and environment variables
- Add shell hook with helpful commands

flake.nix

@@ -16,54 +16,46 @@
 
       # Read versions from package.json
       packageJson = builtins.fromJSON (builtins.readFile ./package.json);
-      versions = {
+      versions = let
+        # Extract version from packageManager string (e.g., "[email protected]+sha512...")
+        pnpmFull = packageJson.packageManager or "[email protected]";
+        pnpmVersion = builtins.head (builtins.match "pnpm@([^+]+).*" pnpmFull);
+      in {
         nodejs = builtins.replaceStrings ["^" "~"] ["" ""] packageJson.engines.node;
-        pnpm = builtins.replaceStrings ["^" "~"] ["" ""] packageJson.engines.pnpm;
+        pnpm = pnpmVersion;
       };
 
-      # Function to fetch and hash a URL
-      fetchUrlHash = url: let
-        file = builtins.fetchurl url;
-        hash = builtins.hashFile "sha256" file;
-      in "sha256-${hash}";
-
-      # Generate hashes for Node.js and pnpm
-      nodeHashes = {
-        darwin-x64 = fetchUrlHash "https://nodejs.org/dist/v${versions.nodejs}/node-v${versions.nodejs}-darwin-x64.tar.gz";
-        darwin-arm64 = fetchUrlHash "https://nodejs.org/dist/v${versions.nodejs}/node-v${versions.nodejs}-darwin-arm64.tar.gz";
-        linux-x64 = fetchUrlHash "https://nodejs.org/dist/v${versions.nodejs}/node-v${versions.nodejs}-linux-x64.tar.gz";
-        linux-arm64 = fetchUrlHash "https://nodejs.org/dist/v${versions.nodejs}/node-v${versions.nodejs}-linux-arm64.tar.gz";
-      };
+      # Function to fetch Node.js tarball with hash
+      fetchNodeJs = version: platform: arch:
+        pkgs.fetchurl {
+          url = "https://nodejs.org/dist/v${version}/node-v${version}-${platform}-${arch}.tar.gz";
+          hash = null; # Nix will provide the correct hash when it fails
+        };
 
-      pnpmHash = fetchUrlHash "https://registry.npmjs.org/pnpm/-/pnpm-${versions.pnpm}.tgz";
+      # Function to fetch pnpm tarball with hash
+      fetchPnpm = version:
+        pkgs.fetchurl {
+          url = "https://registry.npmjs.org/pnpm/-/pnpm-${version}.tgz";
+          hash = null; # Nix will provide the correct hash when it fails
+        };
 
       # Define specific Node.js version
       nodejs = pkgs.stdenv.mkDerivation rec {
         pname = "nodejs";
         version = versions.nodejs;
 
-        src = pkgs.fetchurl {
-          url = "https://nodejs.org/dist/v${version}/node-v${version}-${
+        src =
+          fetchNodeJs version
+          (
             if pkgs.stdenv.isDarwin
             then "darwin"
             else "linux"
-          }-${
+          )
+          (
             if pkgs.stdenv.isx86_64
             then "x64"
             else "arm64"
-          }.tar.gz";
-          hash =
-            nodeHashes
-            ."${
-              if pkgs.stdenv.isDarwin
-              then "darwin"
-              else "linux"
-            }-${
-              if pkgs.stdenv.isx86_64
-              then "x64"
-              else "arm64"
-            }";
-        };
+          );
 
         installPhase = ''
           mkdir -p $out
@@ -81,10 +73,7 @@
         name = "pnpm";
         version = versions.pnpm;
 
-        src = pkgs.fetchurl {
-          url = "https://registry.npmjs.org/pnpm/-/pnpm-${versions.pnpm}.tgz";
-          hash = pnpmHash;
-        };
+        src = fetchPnpm versions.pnpm;
 
         buildInputs = [nodejs];