Add a headless (CI-runnable) test harness for JSONPath and the static filtering parser #4030

Context

npm test in the repo is currently a stub (echo "Error: no test specified" && exit 1). The JSONPath RFC 9535 conformance corpus exists but lives in a browser-only harness (tools/jsonpath-tests.html) that renders results into the DOM, so it can't run in CI. The static network filtering parser has no standalone unit tests despite being logic-dense and actively changed (e.g. the recent "consecutive $$" fix).

Proposal

Add small, dependency-free headless test runners under tools/, using the built-in node:test runner. They import src/js modules directly, so no build step is required:

• Extract the existing JSONPath corpus into a shared data module reused by both the browser harness and a new Node runner (no duplication).
• Add a classification runner for AstFilterParser (network / cosmetic / scriptlet / html / responseheader / error), including a regression group for the consecutive-$$ interpretation.
• Wire npm test to node --test "./tools/*.node.js".

Result on my branch: 64 assertions pass, 17 unsupported-RFC-9535 cases tracked as pending, 0 failures; npm run lint clean.

Question

Would a PR along these lines be welcome? I have it implemented and can open it against master, or adjust the scope/approach to your preference.