Fetch timeout AbortErrors now identifiable in autocapture

1.391.9

Patch Changes

• #3922 26aa9ba Thanks @posthog! - Exception autocapture: posthog-js's own fetch timeout now aborts with an explicit, descriptive reason (PostHog request timed out after <n>ms) instead of a reason-less DOMException: AbortError: signal is aborted without reason. This keeps name === 'AbortError' so existing timeout handling (e.g. feature flag timeout detection) is unchanged, but makes our own timeouts identifiable and stops them being re-captured as noise by console-error exception autocapture. (2026-06-22)