Add CI coverage summaries and aggregate JaCoCo report (#6451)

.github/workflows/build.yml

@@ -185,6 +185,24 @@ jobs:
     uses: ./.github/workflows/dependency-review.yml
     secrets: inherit
 
+  # Coverage aggregate: merges the JUnit + e2e:live + cucumber .exec
+  # artifacts produced by the jobs above into one report, plus pulls
+  # in vitest + Playwright frontend coverage for the per-area matrix.
+  # `if: always()` so a producer failing partway still gets credit
+  # for whatever did record. Advisory only - intentionally NOT in
+  # all-checks-passed, so a flaky aggregate run never blocks merging.
+  coverage-aggregate:
+    if: always()
+    needs:
+      - build
+      - playwright-e2e-live
+      - docker-compose-tests
+      - frontend-validation
+    permissions:
+      contents: read
+    uses: ./.github/workflows/coverage-aggregate.yml
+    secrets: inherit
+
   # Single status check that branch protection should mark as required.
   # Succeeds when every upstream job is either `success` or `skipped` (path-
   # gated jobs that didn't apply this run). Any `failure` or `cancelled`