[aw] Breaking Change Documentation failed

### Workflow Failure

**Workflow:** [Breaking Change Documentation](https://github.com/dotnet/runtime/blob/main/.github/workflows/breaking-change-doc.md)
**Branch:** main
**Run:** https://github.com/dotnet/runtime/actions/runs/33218722021
**Pull Request:** [#132763](https://github.com/dotnet/runtime/pull/132763)

> [!WARNING]
> **Engine Failure**: The `copilot` engine terminated unexpectedly.

**Last agent output:**
```
Changes +0 -0
Duration 3s
Resume copilot --resume=2b9f16ac-7481-4995-abbb-cd105641b007
● Request failed (transient_auth_error). Retrying...
● Request failed (transient_auth_error). Retrying...
Authentication failed with provider at http://172.30.0.30:10002 (HTTP 401).
Check your COPILOT_PROVIDER_API_KEY or COPILOT_PROVIDER_BEARER_TOKEN.
Changes +0 -0
Duration 3s
Resume copilot --resume=b5e0f1f2-e86f-433a-9cdb-237642f37bc8
```

### Action Required

**Assign this issue to an agent** to debug and fix the issue.

Debug with any coding agent

Use this prompt with any coding agent (GitHub Copilot, Claude, Gemini, etc.):

````
Debug the agentic workflow failure using https://raw.githubusercontent.com/github/gh-aw/main/debug.md

The failed workflow run is at https://github.com/dotnet/runtime/actions/runs/33218722021
````

Manually invoke the agent

Debug this workflow failure using your favorite Agent CLI and the `agentic-workflows` prompt.

- Start your agent
- Load the `agentic-workflows` skill from `.github/skills/agentic-workflows/SKILL.md` or
- Type `debug the agentic workflow breaking-change-doc failure in https://github.com/dotnet/runtime/actions/runs/33218722021`

> [!TIP]
>
> Stop reporting this workflow as a failure
>
> To stop a workflow from creating failure issues, set `report-failure-as-issue: false` in its frontmatter:
> ```yaml
> safe-outputs:
> report-failure-as-issue: false
> ```
>
>

> Generated from [Breaking Change Documentation](https://github.com/dotnet/runtime/actions/runs/33218722021) · [◷](https://github.com/search?q=repo%3Adotnet%2Fruntime+is%3Aissue+%22gh-aw-workflow-id%3A+breaking-change-doc%22&type=issues)

Start with .github/workflows/breaking-change-doc.md and the failed run 33218722021. Read .github/skills/agentic-workflows/SKILL.md or debug.md, then investigate the reported copilot authentication failure and its workflow context. Done means the Breaking Change Documentation workflow completes without this engine failure or the failure is correctly prevented from being reported.

Written by the indexing model from the issue text.