Suggested test: copilot/concurrency-job-discriminator-import

## Motivation

github/gh-aw#57978 — Shared workflows can now provide `concurrency.job-discriminator`; the first imported discriminator wins across shared workflows, and the main workflow's discriminator overrides imported values when both are defined. Workflow-level `concurrency.group` remains rejected.

## Proposed test

- **Workflow file**: `test-copilot-concurrency-job-discriminator.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `create-issue`
- **Variant**: standard

## Minimal test prompt sketch

Compile a workflow importing a shared workflow that declares `concurrency.job-discriminator: ${{ inputs.item_id }}`, confirm the discriminator is honored in the generated lock file's concurrency group, then have the agent create an issue confirming the run completed under the expected concurrency group.

## New fixtures or secrets needed

Requires a new shared workflow snippet declaring `concurrency.job-discriminator`. No new secrets needed.

## Notes

Mostly a compile-time assertion on generated YAML `concurrency.group` interpolation; also worth a negative-case check that a workflow declaring plain `concurrency.group` is still rejected, though that may be better suited to gh-aw's own unit tests than this E2E harness.

> Generated by [🔍 Suggest New E2E Tests](https://github.com/githubnext/gh-aw-test/actions/runs/33734461438) · copilot · auto · 19.8 AIC · ⌖ 6.58 AIC · ⊞ 8.8K · [◷](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-concurrency-job-discriminator.md and inspect nearby Copilot E2E tests for their workflow and fixture conventions. Compile the workflow with workflow_dispatch, an imported shared workflow declaring concurrency.job-discriminator, and the create-issue safe output. Done means the generated lock file contains the expected concurrency.group interpolation and the run creates a confirming issue.

Written by the indexing model from the issue text.