Suggested test: copilot/create-pull-request-issues-disabled

## Motivation

Link to gh-aw PR: github/gh-aw#45359 — fix(create_pull_request): redirect fallback issue to alternate repo when target has issues disabled (410).

When a cross-repo PR workflow targets a repo with issues disabled, `createFallbackIssue` received a 410 Gone and hard-failed the entire safe-output step. The fix redirects the fallback to `GH_AW_FAILURE_ISSUE_REPO` or `GITHUB_REPOSITORY`. No regression test exists for this code path.

## Proposed test

- **Workflow file**: `test-copilot-siderepo-create-pull-request-issues-disabled.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `create-pull-request`
- **Variant**: siderepo (cross-repo PR; the target repo needs issues disabled)

## Minimal test prompt sketch

Ask the agent to create a pull request against a target repo that has issues disabled. If a fallback issue would normally be created (e.g. due to an assignee that doesn't exist), the handler should gracefully redirect the fallback issue to the workflow repo rather than failing. The test asserts that the PR is created successfully even when the fallback issue path triggers the 410 redirect.

## New fixtures or secrets needed

Requires a repository with issues disabled in the `githubnext` org (or a new `gh-aw-no-issues` repo). This is the main open question — if an existing fixture already has issues disabled, no new fixture is needed. Otherwise a new repo must be created once.

## Notes

This is distinct from the existing `test-copilot-siderepo-create-pull-request.md` which targets `gh-aw-side-repo` (issues enabled). The new test needs a repo where issues are explicitly disabled to exercise the 410 fallback path. Triage should first check if any existing fixture repo has issues disabled.

> [!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/29320519088) · 18.3 AIC · ⌖ 5.55 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)

First inspect test-copilot-siderepo-create-pull-request.md and check whether an existing githubnext fixture has issues disabled. Add test-copilot-siderepo-create-pull-request-issues-disabled.md with workflow_dispatch, the copilot engine, and the siderepo create-pull-request variant. Done means the test exercises the fallback path and confirms the pull request succeeds when the target returns 410.

Written by the indexing model from the issue text.