docs: Fastify example is no-test — server.listen() blocks, harness only checks compile

[proggeramlug]

Summary

docs/src/stdlib/http.md advertises Fastify as "API-compatible with the npm package", but the example block is marked no-test because server.listen() blocks forever. The doc-tests harness therefore only verifies the example compiles and links — it never actually runs the server, makes a request, or confirms a response.

This means the "API-compatible" claim has no end-to-end test coverage in-repo for the one stdlib module people are most likely to try. Stubs or regressions in any handler / routing / reply path could land without the harness noticing.

Evidence

• Example block in docs/src/stdlib/http.md tagged typescript,no-test with app.listen({ port: 3000 }, ...).
• No matching integration test in test-files/ or crates/perry-stdlib/tests/ that starts a Fastify server and issues an HTTP request against it.

Suggested fix

Add a real integration test — either in test-files/ or as a doc-example test — that:

1. Spawns the Fastify server in a background thread (or spawn_for_promise_deferred).
2. Hits it with fetch from the main thread.
3. Asserts the JSON response body.
4. Shuts the server down cleanly.

Alternatively, expose a server.listen({ port, signal }) shape that takes an AbortController-style cancel so the doc example can exit deterministically, then flip the block off no-test.

Until one of those lands, the stdlib docs should probably qualify "API-compatible" → "partially implemented; see open issues" in the http page.