[ci-scan] Test failure: GC/Regressions/Github/Runtime_129681 fails with coreclr_initialize 0x80004005 on osx x64

## Build Information
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1545348
Build error leg or test failing: coreclr Pri1 Runtime Tests Run osx x64 checked — GC/Regressions/Github/Runtime_129681/Runtime_129681

Pipeline: `runtime-coreclr outerloop` (definition 108), branch `main`. The failure reproduces on both osx.15.amd64 machines behind the plain `osx x64 checked` leg (jobs `e2334af3` / `1132d4aa`) in source build [1545348](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1545348) and persists into follow-up build [1545482](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1545482) (job `31e71870`).

This is a distinct failure mode from the Crossgen2 exit-255 signature tracked by #132037 on the R2R_CG2 osx x64 leg: here the plain (non-R2R) osx x64 leg runs the same test but the runtime host aborts during startup with `coreclr_initialize failed - Error: 0x80004005`. The `Crossgen2 failed with exitcode: 255` line from #132037 does not appear in this log.

## Error Details

```
Running test: GC/Regressions/Github/Runtime_129681/Runtime_129681/Runtime_129681.cmd
External disassembler is not available.
BEGIN: coreclr_initialize failed - Error: 0x80004005
END: coreclr_initialize failed - Error: 0x80004005

Return code: 1
...
Expected: 100
Actual: 255
END EXECUTION - FAILED
Test Harness Exitcode is : 1
```

## Error Message

```json
{
"ErrorMessage": [
"Running test: GC/Regressions/Github/Runtime_129681/Runtime_129681/Runtime_129681.cmd",
"BEGIN: coreclr_initialize failed - Error: 0x80004005"
],
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

## First build it occurred
Observed in source build [1545348](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1545348) (2026-08-08) on both osx x64 machines and again in follow-up build [1545482](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1545482) (2026-08-08) — at least two distinct builds.

## Duplicate search
Searched open and closed issues/KBEs for `Runtime_129681`, `coreclr_initialize failed`, and `0x80004005`: the only existing test-specific KBE is #132037, which matches a different signature (`Crossgen2 failed with exitcode: 255`) on the R2R_CG2 leg and does not match this plain-leg startup failure. Related: dotnet/runtime#132037. No open or merged PR references this signature.

---
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.

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> Generated by [CI Outer-Loop Failure Scanner](https://github.com/dotnet/runtime/actions/runs/31286982339) · 719.9 AIC · ⌖ 16.6 AIC · ⊞ 18.3K · [◷](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
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|0|0|

Start with GC/Regressions/Github/Runtime_129681/Runtime_129681/Runtime_129681.cmd and rerun or inspect the plain osx x64 checked results from builds 1545348 and 1545482. Compare the coreclr_initialize failure with the distinct Crossgen2 failure in #132037. Done means the test starts and completes successfully on both osx x64 machines without the 0x80004005 startup error.

Written by the indexing model from the issue text.