fix!: remove legacy nix run code path causing stderr noise

.claude/settings.local.json

@@ -0,0 +1,5 @@
+{
+  "permissions": {
+    "allow": ["WebFetch(domain:nix.dev)"]
+  }
+}

.github/workflows/test.yml

@@ -54,37 +54,28 @@ jobs:
           script: |
             echo The future is $FUTURE
             [[ -z "${ANSWER}" ]] && exit 1 || exit 0
-  test-legacy-nix:
+  test-no-stderr-noise:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
       - name: Install Nix
         uses: cachix/install-nix-action@v30
         with:
-          nix_path: nixpkgs=channel:release-21.05
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
-      - name: Test Basic Bash Shell
+      - name: Run action with packages
         uses: ./
         with:
-          script: |
-            echo "test!"
-      - name: Test Bash Shell with Packages
-        uses: ./
-        with:
-          packages: hello,docker
+          packages: hello
           script: |
             hello
-            command -v docker
-      - name: Test Bash Shell with Enviroment
-        uses: ./
-        env:
-          FUTURE: now
-          ANSWER: 42
-        with:
-          script: |
-            echo The future is $FUTURE
-            [[ -z "${ANSWER}" ]] && exit 1 || exit 0
+      - name: Assert wrapper does not use legacy nix run
+        run: |
+          if grep -q 'nix run nixpkgs\.' dist/wrapper.sh 2>/dev/null; then
+            echo "FAIL: wrapper.sh contains legacy 'nix run nixpkgs.' invocation"
+            exit 1
+          fi
+          echo "PASS: no legacy nix run pattern found"
 
   test-flakes:
     runs-on: ubuntu-latest

src/main.ts

@@ -21,11 +21,6 @@ export async function run(): Promise<void> {
       ? `./script.sh`
       : `${import.meta.dirname}/script.sh`;
 
-    const wrappedPackages = packages
-      .split(",")
-      .map((pkg) => `nixpkgs.${pkg.trim()}`)
-      .join(" ");
-
     const flakeWrappedPackages = flakesFromDevshell
       ? flakes
       : flakes.split(",").join(" ") ||
@@ -43,24 +38,7 @@ export async function run(): Promise<void> {
     const nixWrapper = `
 set -euo pipefail
 
-verlte() {
-    [  "$1" = "$(echo -e "$1\n$2" | sort -V | head -n1)" ]
-}
-
-verlt() {
-    [ "$1" = "$2" ] && return 1 || verlte $1 $2
-}
-
-nix_version=$(nix --version | awk '{ print $3 }')
-
-if verlt $nix_version 2.4
-then
-  # before nix 2.4: nix run
-  nix run ${wrappedPackages} -c ${interpreter} ${scriptPath}
-else
-  # nix 2.4 and later: nix shell
 nix --experimental-features 'nix-command flakes' ${nixCommand} ${flakeWrappedPackages} -c ${interpreter} ${scriptPath}
-fi
       `;
 
     const wrappedScript = `