feat: add go mod tidy verification step

Author: mjfwebb

.github/workflows/build-and-test.yml

@@ -32,6 +32,11 @@ jobs:
         run: |
           git diff --exit-code || (echo "Generated mocks are not up-to-date. Please run 'go generate ./...' locally and push the updated files." && exit 1)
 
+      - name: Verify go.mod is tidy
+        run: |
+          go mod tidy
+          git diff --exit-code || (echo "go.mod or go.sum is not tidy. Please run 'go mod tidy' locally and push the updated files." && exit 1)
+
       - name: Run golangci-lint
         uses: golangci/golangci-lint-action@4afd733a84b1f43292c63897423277bb7f4313a9 # v8
         with: