Suggested test: copilot/dispatch-workflow-single-target-inference

## Motivation

Link to the gh-aw PR: github/gh-aw#48317 — Restore backward compatibility for single-target `dispatch_workflow` safe outputs

When a workflow configures exactly one `dispatch_workflow.workflows` entry, an agent can omit `workflow_name` from the safe-output item and gh-aw should infer it automatically. PR #48317 fixed a regression where this previously-valid omission was rejected. No regression test exists.

## Proposed test

- **Workflow file**: `test-copilot-dispatch-workflow-single-target.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `dispatch_workflow` with a single workflow configured and no explicit `workflow_name` in the agent's output
- **Variant**: standard

## Minimal test prompt sketch

Configure one target workflow in `safe-outputs.dispatch-workflow.workflows`. Instruct the agent to emit a `dispatch_workflow` safe-output item without specifying `workflow_name`. The harness asserts that the dispatch was accepted and the correct workflow was triggered.

## New fixtures or secrets needed

Requires a dispatchable target workflow in `githubnext/gh-aw-test`. The existing `test-copilot-dispatch-workflow.md` or a lightweight stub could serve as the target. No new secrets needed.

## Notes

The existing `test-copilot-dispatch-workflow` test covers multi-target dispatch. This test specifically covers the single-target name-inference path to prevent regression of the #48317 fix.

> Generated by [🔍 Suggest New E2E Tests](https://github.com/githubnext/gh-aw-test/actions/runs/30346216775) · sonnet46 · 24.7 AIC · ⌖ 5.9 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 by reading test-copilot-dispatch-workflow.md and the proposed test-copilot-dispatch-workflow-single-target.md fixture pattern. Configure one dispatchable target workflow in githubnext/gh-aw-test, use the workflow_dispatch trigger and copilot engine, and have the harness verify that an output without workflow_name dispatches the configured target successfully.

Written by the indexing model from the issue text.