proxy: don't mark ingest.queue_send spans ERROR for expected 4xx body rejections

[arseniycodes]

Problem

When a client sends an empty or oversized OTLP body, enqueueStream throws EmptyBodyError / PayloadTooLargeError. These are handled client errors: the outer catch maps them to 400/413 via handleIngestBodyError, the S3 multipart upload is aborted for the oversized case, and the request lifecycle completes normally. But the inner catch inside the ingest.queue_send span unconditionally called recordException + setStatus(ERROR), so every such request produced an ERROR span — and a false-positive incident — for an operation working exactly as designed. The surrounding spans (ingest.forward, auth.validate, the server span) all stay Unset, confirming nothing actually failed.

Fix

• body-capture.ts: new isExpectedBodyError(err) predicate next to the two error classes.
• index.ts: the ingest.queue_send catch skips recordException/setStatus(ERROR) for expected rejections and still rethrows so the outer handler produces the 4xx. Genuine enqueue failures (SQS/S3 errors) are unchanged and still mark the span ERROR.

Testing

• New isExpectedBodyError unit test in body-capture.test.ts (matches both rejections, rejects generic errors/undefined) — written first, red, then green.
• Full proxy suite: tsx --test src/*.test.ts — 89 pass, 0 fail.
• tsc --noEmit clean.

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Summary by cubic

Stop marking ingest.queue_send spans as ERROR for expected 4xx body rejections (empty or oversized OTLP payloads). This removes false-positive incidents while keeping real SQS/S3 enqueue failures marked as ERROR.

• Bug Fixes
  • Added isExpectedBodyError alongside EmptyBodyError and PayloadTooLargeError.
  • Updated index.ts to skip recordException and setStatus(ERROR) for expected rejections; still rethrows so the outer handler returns 400/413.
  • Added unit test for isExpectedBodyError; full proxy test suite passes.

^{Written for commit 3025064. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files

_{Re-trigger cubic}