Fix CI: Use v0.1.5 jsonpath_test.go and fix workflow

- Replace duplicate-prone jsonpath_test.go with clean v0.1.5 version
- Fix ci.yml: use staticcheck via go install instead of non-existent action

Author: oliveagle

.github/workflows/ci.yml

@@ -69,12 +69,11 @@ jobs:
             exit 1
           fi
 
+      - name: Install staticcheck
+        run: go install honnef.co/go/tools/cmd/staticcheck@latest
+
       - name: Run staticcheck
-        uses: dominantv/ci-staticcheck-action@latest
-        with:
-          version: latest
-          packages: ./...
-          flags: -checks=all
+        run: staticcheck ./...
 
   benchmark:
     runs-on: ubuntu-latest