[superlog] Don't mark ingest.queue_send span as ERROR for empty/oversized client bodies

[superlog-app]

Summary

The proxy's ingest.queue_send OTel span was marking ALL exceptions as ERROR before rethrowing, including EmptyBodyError and PayloadTooLargeError. These are expected client-side conditions (empty OTLP payload, body over the size cap) that the outer handleIngestBodyError handler converts into correct 4xx HTTP responses — so no data is lost and the client is informed. The ERROR span label was a false positive that caused Superlog's worker to fingerprint each occurrence as an issue and open recurring incidents.

The pre-auth Content-Length: 0 guard added in #129 fast-rejects the most common form of empty bodies, but explicitly does not cover chunked/undeclared-length empty bodies, which still reach captureBody and trigger this path.

The fix skips recordException/setStatus(ERROR) on the ingest.queue_send span when the error is EmptyBodyError or PayloadTooLargeError. Unexpected server-side errors still record as ERROR as before. An alternative approach would be to silence the incident entirely via Superlog's noise-classification feature, but fixing the span label is cleaner and avoids masking real future errors that happen to share the same span name.

Incident on Superlog

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Summary by cubic

Stop marking the ingest.queue_send OTel span as ERROR for empty or oversized client bodies to eliminate false error noise and recurring incidents while keeping 4xx paths clean.

• Bug Fixes
  • Skip recordException and setStatus(ERROR) for EmptyBodyError and PayloadTooLargeError.
  • Preserve ERROR reporting for unexpected server-side faults.
  • Handles empty chunked bodies that bypass the pre-auth Content-Length: 0 check.

^{Written for commit 5966cd6. Summary will update on new commits.}