fix: use unique MPE ID per E2E run

Replace static migTEST0000001 with mig${github.run_id} so each
workflow run creates uniquely named resources. Prevents 'already exists'
errors when runs overlap or teardown is incomplete.

Author: ngjinshan

.github/workflows/e2e.yml

@@ -19,9 +19,10 @@ defaults:
 
 env:
   PR_NUMBER: ${{ github.event.pull_request.number }}
-  # MPE_ID drives the expected tag value.  Stored as a secret so the real
-  # test MPE is not hard-coded here; falls back to migTEST0000001 for forks.
-  MPE_ID: ${{ secrets.TEST_MPE_ID || 'migTEST0000001' }}
+  # MPE_ID drives the expected tag value.  Uses the unique run ID so every
+  # workflow run gets its own resource names — no collisions between
+  # concurrent or overlapping runs.
+  MPE_ID: mig${{ github.run_id }}
   STACK_NAME: map-auto-tagger-e2e-pr${{ github.event.pull_request.number }}
 
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