* feat(posthog): correlate task events with Go logs via request_id
Auto-injects server request_id into all PostHog server events from
AsyncLocalStorage context. Adds task_request_started client event fired
when SSE traceparent response header arrives, carrying the trace ID used
by Go for log correlation. task_generation_aborted now includes the
in-flight request_id when available.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
* improvement(posthog): tighten trace ID parse and verbose comments
* fix(posthog): use traceparent header as canonical request_id source
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Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
