bug: `gh aw compile` should validate required `workflows:` field on `workflow_run` trigger

[Calidus]

gh aw compile should validate required workflows: field on workflow_run trigger

Summary

gh aw compile --strict silently produces a valid .lock.yml file even when the .md source defines a workflow_run trigger without the required workflows: field. GitHub Actions immediately rejects the resulting workflow with:

on.workflow_run does not reference any workflows.

The compiler should catch this at compile time rather than letting it ship broken.

Reproduction

1. Create an agentic workflow .md with this on: block:

   on:
     workflow_run:
       types: [completed]
       branches:
         - master
   (Note: no workflows: key)
   

2. Run gh aw compile (even with --strict)
3. Compilation succeeds and produces a .lock.yml
4. Push to GitHub — every run fails immediately with 0 jobs and the validation error above

Expected behavior

gh aw compile should error (especially in strict mode) when on.workflow_run is missing the workflows: field, since the resulting workflow file can never successfully trigger.

References

• GitHub docs: https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#workflow_run
• Compiler version: v0.71.5

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