perf(browserless): retry only transient context reset errors

[Kikobeats]

Note

Low Risk
Low risk: narrows retry behavior to a single known transient error code and adds targeted tests; main risk is reduced resiliency if other errors were previously (incorrectly) being masked by retries.

Overview
withPage now retries only when the failure is a transient browser-context connection reset (EBRWSRCONTEXTCONNRESET), and immediately rethrows any other error instead of recreating the context and retrying.

Adds test coverage to ensure non-transient errors are not retried and that transient context disconnections do retry and recover.

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