Suggested test: copilot/add-labels-on-pull-request

> [!WARNING]
> **Threat Detection Engine Failure** — The analysis engine could not complete. This is a tooling failure, not a security finding.
>
>
>
> What happened
>
> The threat detection results could not be parsed.
>
> Review the [workflow run logs](https://github.com/githubnext/gh-aw-test/actions/runs/31162929773) for details.
>

## Motivation

Link to the gh-aw PR: github/gh-aw#50910 — add_labels intent path unconditionally called the `updateIssue` GraphQL mutation, which rejects PR node IDs; fixed by routing PR targets through `updatePullRequest`.

## Proposed test

- **Workflow file**: `test-copilot-add-labels-pull-request.md`
- **Trigger**: `pull_request: [opened, reopened]` guarded by an e2e-marker in the PR body, matching the pattern of `test-copilot-add-labels.md`
- **Engine**: copilot
- **Safe output**: `add-labels` with intent metadata (rationale/confidence) enabled so the handler takes the GraphQL intent path rather than the plain REST path
- **Variant**: standard

## Minimal test prompt sketch

Open (or dispatch against) a pull request instead of an issue; ask the agent to add a label to the triggering PR. Assert the label is applied successfully via the `updatePullRequest` mutation rather than failing with a GraphQL type error.

## New fixtures or secrets needed

None — reuse `githubnext/gh-aw-test`; may need a throwaway branch/PR opened by the dispatcher similar to other PR-triggered tests.

## Notes

All existing `add-labels` tests (`test-copilot-add-labels.md`, `test-copilot-nosandbox-add-labels.md`, `test-copilot-siderepo-add-labels.md`) target issues only — none exercises labeling a pull request, so this is the first regression coverage for the `updatePullRequest` code path.

> Generated by [🔍 Suggest New E2E Tests](https://github.com/githubnext/gh-aw-test/actions/runs/31162929773) · auto · 34.6 AIC · ⊞ 8.3K · [◷](https://github.com/search?q=repo%3Agithubnext%2Fgh-aw-test+is%3Aissue+%22gh-aw-workflow-call-id%3A+githubnext%2Fgh-aw-test%2Fsuggest-new-e2e-tests%22&type=issues)