test: assert env var directly instead of relying on pnpm runtime behavior

The previous version of this test self-updated to pnpm 10.33.0 and expected
pnpm --version to fail under devEngines.onFail=error. But pnpm v10 only reads
the packageManager field, not devEngines, so the check never fired and the
test failed.

Switch the assertion to the contract the af8e203 scope fix actually enforces:
when an explicit version: is supplied, pnpm_config_pm_on_fail must not be
exported by the action. That's deterministic and pnpm-version-agnostic.

.github/workflows/test.yaml

@@ -110,13 +110,16 @@ jobs:
           - label: 'devEngines onFail=error, range (#252)'
             manifest: '{"devEngines":{"packageManager":{"name":"pnpm","version":">=9.15.0","onFail":"error"}}}'
             version: '>=9.15.0'
-          - label: 'devEngines onFail=error + explicit version mismatch keeps strictness'
+          - label: 'explicit version: pnpm_config_pm_on_fail not exported'
             # Regression guard for the af8e203 scope fix: when the user passes an
             # explicit `version:` input, the action must NOT export
-            # pnpm_config_pm_on_fail=download, so `onFail=error` still fires.
+            # pnpm_config_pm_on_fail=download, so the user's strict onFail policy
+            # is preserved. Asserted directly on the env var rather than pnpm
+            # runtime behavior — different pnpm majors read devEngines
+            # differently (v10 ignores it, v11+ honors it).
             manifest: '{"devEngines":{"packageManager":{"name":"pnpm","version":"9.15.5","onFail":"error"}}}'
             explicit_version: '10.33.0'
-            expect_pnpm_error: true
+            expect_pm_on_fail_unset: true
 
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
@@ -131,7 +134,7 @@ jobs:
           version: ${{ matrix.explicit_version }}
 
       - name: 'Test: pnpm reports the pinned version'
-        if: ${{ !matrix.expect_pnpm_error }}
+        if: ${{ !matrix.expect_pm_on_fail_unset }}
         env:
           REQUIRED: ${{ matrix.version }}
         run: |
@@ -152,17 +155,14 @@ jobs:
           fi
         shell: bash
 
-      - name: 'Test: pnpm exits non-zero (onFail=error strictness preserved)'
-        if: ${{ matrix.expect_pnpm_error }}
+      - name: 'Test: pnpm_config_pm_on_fail not exported (explicit version preserves strict policy)'
+        if: ${{ matrix.expect_pm_on_fail_unset }}
         run: |
-          set +e
-          out="$(pnpm --version 2>&1)"
-          rc=$?
-          echo "${out}"
-          if [ $rc -eq 0 ]; then
-            echo "Expected pnpm --version to fail (devEngines.onFail=error mismatch), but it exited 0"
+          if [ -n "${pnpm_config_pm_on_fail:-}" ]; then
+            echo "Expected pnpm_config_pm_on_fail to be unset, but got: '${pnpm_config_pm_on_fail}'"
             exit 1
           fi
+          echo "pnpm_config_pm_on_fail is unset, as expected"
         shell: bash
 
   standalone: