[ci-scan] Test failure: tracing/eventpipe/nonlossyblockenv drops events on interpreter

## Build Information
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1588980
Build error leg or test failing: coreclr Pri1 Runtime Tests Run linux x64 checked-tracing/eventpipe/nonlossyblockenv

KBE authoring guidance (ci-failure-scan)

- `Error Details` is for readers. Paste the full exception, stack trace, or build error excerpt so the failure is understandable without opening the raw log.
- Build Analysis parses only the single JSON block under `Error Message`.
- `ErrorMessage` is a case-sensitive ordinal `String.Contains` substring copied verbatim from the failing log.
- Set `BuildRetry` to `true` only for a clear infrastructure retry case. `ExcludeConsoleLog` disables Helix console-log scanning.

## Error Details

On the `runtime-interpreter` pipeline the eventpipe tracing test `tracing/eventpipe/nonlossyblockenv/nonlossyblockenv.cmd` fails: the non-lossy (block) buffering scenario expects zero dropped events but the trace reports a large `EventsLost` count under the interpreter. The `tracing` Helix work item fails across many legs (linux x64/arm64, windows x64/arm64, osx x64/arm64). Observed in source build 1588980 (finished 2026-09-09) and still reproduces in follow-up build 1592662 (finished 2026-09-11).

```
Observed 50000 'NonLossyBlockEnvEventSource' events; EventsLost = 270.
FAILED: expected zero dropped events, but the trace reported 270.
==TEST FINISHED: FAILED!==
Expected: 100
Actual: 255
END EXECUTION - FAILED
at Xunit.Assert.True(Nullable`1 condition, String userMessage) ...
14:21:59.682 Failed test: tracing/eventpipe/nonlossyblockenv/nonlossyblockenv/nonlossyblockenv.cmd
```

## Error Message

```json
{
"ErrorMessage": [
"Running test: tracing/eventpipe/nonlossyblockenv/nonlossyblockenv/nonlossyblockenv.cmd",
"FAILED: expected zero dropped events, but the trace reported"
],
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

Agentic workflow metadata (ci-failure-scan)

Workflow artifact: ci-failure-scan
Artifact kind: kbe-verification
Verified match count: 1 hits in failure.log

---
Filed by [`ci-failure-scan`](https://github.com/dotnet/runtime/blob/main/.github/workflows/ci-failure-scan.md) (detection only). [`ci-failure-fix`](https://github.com/dotnet/runtime/blob/main/.github/workflows/ci-failure-fix.md) walks open `[ci-scan]` KBEs and either opens a small fix PR or comments here to loop in owners — it never disables the test.

> Generated by [CI Outer-Loop Failure Scanner](https://github.com/dotnet/runtime/actions/runs/34845246760) · opus48 · 996.1 AIC · ⌖ 13.1 AIC · ⊞ 19.7K · [◷](https://github.com/search?q=repo%3Adotnet%2Fruntime+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Fruntime%2Fci-failure-scan%22&type=issues)

### Report

|Build|Repository|Test|Pull Request|
|---|---|---|---|
|[1597012](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1597012)|dotnet/runtime|[tracing/eventpipe/nonlossyblockenv/nonlossyblockenv/nonlossyblockenv.cmd](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1597012&view=ms.vss-test-web.build-test-results-tab&runId=44087580&resultId=115085)||
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|1|1|1|

Start with tracing/eventpipe/nonlossyblockenv/nonlossyblockenv.cmd and the linked failing build logs. Reproduce the interpreter test and inspect how the non-lossy block-buffering scenario counts EventsLost across the listed platforms. Done means the test completes with zero dropped events; the issue is already assigned.

Written by the indexing model from the issue text.