fix(function): access to response

[Kikobeats]

Note

Medium Risk
Touches the isolated-function template and invocation options to plumb a new response object through, which could subtly affect user function argument shaping and runtime behavior.

Overview
Adds support for accessing the initial navigation HTTPResponse from browserless functions via a new response argument.

goto now returns { device, response }; the response is serialized in index.js and passed into the isolated runtime as _response, and template.js reconstructs it into a Puppeteer-like API (callable methods) while ensuring _response isn’t leaked into user opts.

Extends the test suite to cover response access with and without page, correct serialization/reconstruction behavior, and the undefined case when no response is returned.

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