Suggested test: copilot/create-pull-request-with-labels

## Motivation

Link to the gh-aw PR: github/gh-aw#48100 — Fix `mcp-cli` per-field stdin mode: when an agent piped a full JSON payload with `--body .`, the entire JSON string was assigned as the field value instead of extracting the named field. This affected `create_pull_request` (which has an `array`-typed `labels` field, triggering JSON mode).

## Proposed test

- **Workflow file**: `test-copilot-create-pull-request-labels.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `create-pull-request`
- **Variant**: standard

## Minimal test prompt sketch

The agent creates a pull request and the `safe-outputs` block configures `labels` as a non-empty array. The test verifies that the PR is created with the correct label(s) attached — confirming that per-field stdin JSON extraction works correctly rather than embedding raw JSON into the PR body.

## New fixtures or secrets needed

None — the existing `githubnext/gh-aw-test` repo supports PR creation. A pre-existing branch is not required; `create-pull-request` can push to a new branch via the safe-output.

## Notes

The existing `test-copilot-create-pull-request.md` test does not assert on label values. A dedicated test that includes a `labels` array in the safe-output config would catch any regression of the per-field stdin extraction bug fixed in #48100.

> Generated by [🔍 Suggest New E2E Tests](https://github.com/githubnext/gh-aw-test/actions/runs/30196033978) · sonnet46 · 30 AIC · ⌖ 8.78 AIC · ⊞ 6.1K · [◷](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)

Start with the existing test-copilot-create-pull-request.md workflow and compare it with the proposed test-copilot-create-pull-request-labels.md file. Configure a workflow_dispatch test using the copilot engine and create-pull-request safe output with a non-empty labels array. Done means the resulting pull request in githubnext/gh-aw-test has the expected label attached and the test catches raw JSON being used as the value.

Written by the indexing model from the issue text.