test(env-virtual): execute pkgmgr from Python venv instead of system launcher

The virtual environment test no longer invokes the distro-installed pkgmgr launcher (Nix-based).
Instead, it explicitly installs and activates the Python venv via make setup-venv and runs pkgmgr from there.

This aligns the test with its actual purpose (venv validation), avoids accidental execution of the Nix launcher, and fixes the failure caused by the missing run_with_github_403_retry helper in the venv workflow.

https://chatgpt.com/share/693ee224-e838-800f-8fa0-45295b2f5e20

scripts/test/test-env-virtual.sh

@@ -1,32 +1,49 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-IMAGE="pkgmgr-$PKGMGR_DISTRO"
+IMAGE="pkgmgr-${PKGMGR_DISTRO}"
 
 echo
 echo "------------------------------------------------------------"
-echo ">>> Testing VENV: $IMAGE"
+echo ">>> Testing VENV: ${IMAGE}"
 echo "------------------------------------------------------------"
+
 echo "[test-env-virtual] Inspect image metadata:"
-docker image inspect "$IMAGE" | sed -n '1,40p'
-
-echo "[test-env-virtual] Running: docker run --rm --entrypoint pkgmgr $IMAGE --help"
+docker image inspect "${IMAGE}" | sed -n '1,40p'
 echo
 
-# Run the command and capture the output
+# ------------------------------------------------------------
+# Run VENV-based pkgmgr test inside container
+# ------------------------------------------------------------
 if OUTPUT=$(docker run --rm \
     -e REINSTALL_PKGMGR=1 \
-        -v "pkgmgr_nix_store_${PKGMGR_DISTRO}:/nix" \
     -v "$(pwd):/src" \
-        -v "pkgmgr_nix_cache_${PKGMGR_DISTRO}:/root/.cache/nix" \
-        "$IMAGE" 2>&1); then
+    -w /src \
+    "${IMAGE}" \
+    bash -lc '
+        set -euo pipefail
+
+        echo "[test-env-virtual] Installing pkgmgr (distro package)..."
+        make install
+
+        echo "[test-env-virtual] Setting up Python venv..."
+        make setup-venv
+
+        echo "[test-env-virtual] Activating venv..."
+        . "$HOME/.venvs/pkgmgr/bin/activate"
+
+        echo "[test-env-virtual] Using pkgmgr from:"
+        command -v pkgmgr
+        pkgmgr --help
+    ' 2>&1); then
+
     echo "$OUTPUT"
     echo
-    echo "[test-env-virtual] SUCCESS: $IMAGE responded to 'pkgmgr --help'"
+    echo "[test-env-virtual] SUCCESS: venv-based pkgmgr works in ${IMAGE}"
 
 else
     echo "$OUTPUT"
     echo
-    echo "[test-env-virtual] ERROR: $IMAGE failed to run 'pkgmgr --help'"
+    echo "[test-env-virtual] ERROR: venv-based pkgmgr failed in ${IMAGE}"
     exit 1
 fi