ci: control run — build v1.3.4 (pre-fix) under empty java_home to confirm cascade

Author: pzalutski-pixel

.github/workflows/repro-issue18.yml

@@ -13,8 +13,10 @@ jobs:
     runs-on: macos-latest
 
     steps:
-    - name: Checkout
+    - name: Checkout v1.3.4 source (CONTROL — pre-ensurer; expect the cascade to reproduce)
       uses: actions/checkout@v4
+      with:
+        ref: v1.3.4
 
     # Temurin is only used to RUN the Maven build. The JavaLens product itself
     # is later launched under a SDKMAN-managed Corretto JVM (the reporter's setup).