Suggested test: copilot/engine-model-with-max-ai-credits

## Motivation

Link to the gh-aw PR: github/gh-aw#48482 — Fix imported `engine.model` silently dropped when `max-ai-credits` is set

When a workflow sets `max-ai-credits` at the top level and also pins `engine.model` (whether directly or via `@import`), the model pin was silently discarded before this fix. No regression test covers the combination of `max-ai-credits` + explicit model selection.

## Proposed test

- **Workflow file**: `test-copilot-engine-model-with-max-ai-credits.md`
- **Trigger**: `workflow_dispatch`
- **Engine**: copilot
- **Safe output**: `create-issue` (minimal, to confirm the workflow ran without falling back to the default model expression)
- **Variant**: standard

## Minimal test prompt sketch

Write a workflow that sets both `max-ai-credits: 50` and an explicit `engine.model` pin in frontmatter. Instruct the agent to create a trivial issue. The compiled lockfile should embed the pinned model literal (not the `${{ vars.GH_AW_MODEL_AGENT_COPILOT || ... }}` fallback expression), which the test runner can verify by inspecting the generated `.lock.yml`.

## New fixtures or secrets needed

None. Standard repo is sufficient; model pin can be any valid model string (e.g. `claude-sonnet-4.6`).

## Notes

The lockfile assertion (checking that the compiled model expression is not the dynamic vars fallback) could be done in `e2e.sh` as a compile-time check rather than a live-run check, making this test cheap to run. This complements the existing `test-copilot-dispatch-workflow` and `test-copilot-call-workflow` coverage.

> 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 with the proposed test-copilot-engine-model-with-max-ai-credits.md workflow and compare it with test-copilot-dispatch-workflow and test-copilot-call-workflow. Use e2e.sh to see how compiled .lock.yml files are checked. Done means the workflow sets max-ai-credits and an explicit copilot engine.model, and the lockfile contains the pinned model literal rather than the dynamic fallback expression.

Written by the indexing model from the issue text.