Suggested test: copilot/submit-pull-request-review-suggestion-syntax

## Motivation

Link to the gh-aw PR: github/gh-aw#47508 — feat: use GitHub suggestion syntax in PR reviewer comments

The PR review safe-output now supports emitting code fixes in GitHub suggestion syntax (` ``` suggestion ``` ` blocks) instead of collapsed `` blocks. There is no test covering this new output format.

## Proposed test

- **Workflow file**: `test-copilot-submit-pull-request-review-suggestion-syntax.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `submit-pull-request-review`
- **Variant**: standard

## Minimal test prompt sketch

Given an open pull request that changes a single line of code, ask the agent to review it and suggest an alternative implementation using GitHub suggestion syntax. Assert that the submitted review body contains at least one `suggestion` fenced code block.

## New fixtures or secrets needed

None — an existing open test PR in `githubnext/gh-aw-test` (created by another test) is sufficient.

## Notes

Existing `test-copilot-submit-pull-request-review.md` covers the base review submission flow but does not verify suggestion-syntax output. This would be an additive coverage test for the new feature.

> [!WARNING]
>
> Firewall blocked 1 domain
>
> The following domain was blocked by the firewall during workflow execution:
>
> - `awmgmcpg`
>> To allow these domains, add them to the `network.allowed` list in your workflow frontmatter:
>
> ```yaml
> network:
> allowed:
> - defaults
> - "awmgmcpg"
> ```
>
> See [Network Configuration](https://github.github.com/gh-aw/reference/network/) for more information.
>
>

> Generated by [🔍 Suggest New E2E Tests](https://github.com/githubnext/gh-aw-test/actions/runs/29994494559) · sonnet46 22.2 AIC · ⌖ 5.72 AIC · ⊞ 5.7K · [◷](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 by comparing test-copilot-submit-pull-request-review-suggestion-syntax.md with the existing test-copilot-submit-pull-request-review.md and reviewing the gh-aw PR linked in the issue. Run the new workflow against the existing open test PR; it is done when the submitted review body contains at least one fenced suggestion code block.

Written by the indexing model from the issue text.