Suggested test: copilot/disclosure-header

## Motivation

Link to the gh-aw PR: github/gh-aw#44497 — Add `disclosure-header` message for AI authorship disclosure in safe-outputs

This PR introduced a new `messages.disclosure-header` frontmatter field that prepends a built-in AI authorship notice to every safe-output body. No existing test exercises this opt-in field.

## Proposed test

- **Workflow file**: `test-copilot-disclosure-header.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `create-issue`
- **Variant**: standard

## Minimal test prompt sketch

Ask the agent to create a GitHub issue with a short title and body. The workflow frontmatter should set `messages.disclosure-header: true`. The test should assert that the created issue body begins with the built-in AI authorship disclosure text prepended automatically by gh-aw.

## New fixtures or secrets needed

None — `create-issue` against `githubnext/gh-aw-test` is already exercised by existing tests.

## Notes

The existing `test-copilot-create-issue.md` does not set `messages.disclosure-header`, so this is net-new coverage. A `samples:` block can be used for deterministic runs since the sample value is the agent body content before header injection.

> [!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/29083912426) · 20.8 AIC · ⌖ 5.52 AIC · ⊞ 5.6K · [◷](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-disclosure-header.md with the existing test-copilot-create-issue.md workflow. Set the workflow to use copilot, workflow_dispatch, create-issue, and messages.disclosure-header: true, using samples if needed for deterministic output. Done means the created issue body begins with the built-in AI authorship disclosure, with no new secrets or fixtures required.

Written by the indexing model from the issue text.