Puppeteer's first CDP call after connect is Target.getBrowserContexts.
When the single cdp_processor is busy (e.g. Page.navigate with fetch
interception), queued Target commands stall and Puppeteer hits
protocolTimeout on getBrowserContexts before any user code runs.
Answer getBrowserContexts synchronously in fast_path_response with the
same payload as domains::target::handle (default context id "default"),
matching Browser context initialization in CdpContext.
Co-authored-by: Obscura Contributor <contributor@users.noreply.github.com>
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