Suggested test: copilot/push-to-pull-request-branch-no-fallback

## Motivation

Link to the gh-aw PR: github/gh-aw#59739 — Request PR read access for no-fallback branch pushes

## Proposed test

- **Workflow file**: `test-copilot-push-to-pull-request-branch-no-fallback.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `push-to-pull-request-branch`
- **Variant**: standard

## Minimal test prompt sketch

Configure `push-to-pull-request-branch` with `fallback-as-pull-request: false` and a `target:` PR number (mirroring `test-copilot-push-to-pull-request-branch-using-dispatch.md`). The agent creates a small file and pushes it to the target PR branch. The test asserts the push succeeds — regression coverage for the fix where GitHub App tokens previously omitted `pull-requests: read`, causing a 403 on PR metadata lookup when fallback was disabled.

## New fixtures or secrets needed

None — reuses the existing dispatch-triggered PR pattern; needs an open PR fixture at dispatch time just like the current dispatch test.

## Notes

No existing test sets `fallback-as-pull-request: false` (checked via grep across all `test-*push-to-pull-request-branch*.md`). This isolates the permission-generation regression from PR #59739 rather than general push-to-pull-request-branch behavior, which is already covered.

> Generated by [🔍 Suggest New E2E Tests](https://github.com/githubnext/gh-aw-test/actions/runs/34456199311) · copilot · auto · 54.6 AIC · ⌖ 6.16 AIC · ⊞ 8.4K · [◷](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 test-copilot-push-to-pull-request-branch-using-dispatch.md and compare it with the proposed test-copilot-push-to-pull-request-branch-no-fallback.md workflow. Run the dispatch-triggered test with an open PR fixture, and consider the work done when the agent pushes to the target PR branch successfully with fallback-as-pull-request: false and no new fixtures or secrets.

Written by the indexing model from the issue text.