fix: CI coverage upload conflicts and matrix handling

- Only run coverage on Node 20 (not all matrix nodes)
- Use unique artifact names per node version
- Add retention-days to prevent artifact buildup
- Run regular tests on Node 18 and 22

Author: thegreatalxx

.github/workflows/ci.yml

@@ -33,14 +33,20 @@ jobs:
         run: npm run build
 
       - name: Run tests with coverage
+        if: matrix.node-version == 20
         run: npm run test:coverage
 
+      - name: Run tests
+        if: matrix.node-version != 20
+        run: npm test
+
       - name: Upload coverage report
+        if: matrix.node-version == 20 && always()
         uses: actions/upload-artifact@v4
-        if: always()
         with:
-          name: coverage-report
+          name: coverage-report-node-${{ matrix.node-version }}
           path: coverage/
+          retention-days: 7
 
       - name: Verify dist output
         run: |