fix: prevent crash when Node rejects Set-Cookie header

[wwhsaber]

What

Prevent process crashes when a response sets a cookie value that Node rejects (for example non-ASCII characters that pass statehood validation but fail res.setHeader with ERR_INVALID_CHAR).

Why

When writeHead fails because of an invalid Set-Cookie value, exports.send recovers by calling internals.fail() to send a 500. The fail path re-runs the route marshal cycle, which re-applies pending request._states and re-emits the same bad cookie. The second setHeader throws again and is not recovered, so Node crashes.

This was reported in #4527 with values like Cyrillic cookie contents ("тест").

Changes

• In lib/transmit.js exports.send catch path: clear request._states before recovering with internals.fail(), so the error response does not re-apply rejected cookies.
• Add a regression test in test/state.js covering a non-ASCII cookie value that Node rejects.

Verification

# Repro (before fix: process crash; after fix: HTTP 500)
node -e '
const Hapi = require("./");
(async () => {
  const server = Hapi.server({ debug: false });
  server.route({
    method: "GET",
    path: "/",
    handler: (request, h) => h.response("ok").state("cookieName2", "тест")
  });
  const res = await server.inject("/");
  console.log(res.statusCode, res.headers["set-cookie"], res.result);
})();
'

# Targeted suites
npx lab -a @hapi/code -m 5000 test/state.js test/transmit.js
# 115 tests complete

Observed after fix:

• status 500
• no set-cookie header
• standard internal server error payload
• process does not crash

Closes #4527