Store the coverage file as an artifact

Author: nevinera

.github/workflows/ci.yml

@@ -83,6 +83,13 @@ jobs:
       - run: bundle install --standalone
       - run: bundle binstubs --all
       - run: script/run_build
+      - name: Store coverage output for reference
+        uses: actions/upload-artifact@v4
+        if: failure()
+        with:
+          name: coverage-report-${{ matrix.ruby }}
+          path: coverage/index.html
+          retention-days: 14
 
   legacy:
     name: Legacy Ruby Builds (${{ matrix.container.version }})