[plan] Add fork context hint to workflow failure conclusion messages

[github-actions]

Context

Closes part of #18481 — gh-aw in forks.

When a gh-aw workflow fails in a fork due to missing secrets, the conclusion/failure job opens a GitHub issue or posts a comment with a generic error (e.g., "API key not found"). There is no mention of fork context as a likely cause, making debugging very hard for fork users.

Objective

Update the conclusion job's failure reporter to include a fork-context hint when github.event.repository.fork == true.

Approach

1. Locate where the conclusion job generates the failure issue body. This is likely in a .cjs file under actions/setup/js/ (e.g., conclusion.cjs or similar) or in the compiled workflow YAML directly.
2. Add a check: if context.payload.repository.fork === true (or the equivalent GitHub Actions expression ${{ github.event.repository.fork }}), append a fork hint to the failure message:

   💡 This repository is a fork. If this failure is due to missing API keys or tokens, note that secrets from the parent repository are not inherited. Configure the required secrets directly in your fork's Settings → Secrets and variables → Actions.

3. The hint should appear in the body of any issue or comment opened by the conclusion job on failure.
4. Run make fmt-cjs && make lint-cjs to validate JS changes; run make recompile if workflow YAML was touched.

Files to Modify

• Relevant .cjs file(s) under actions/setup/js/ that generate failure issue/comment bodies
• Any associated test files

Acceptance Criteria

• Fork hint is appended to failure issue/comment body when repository.fork === true
• Hint clearly explains that secrets must be configured in the fork
• Normal (non-fork) failure messages are unchanged
• Linting passes
  Related to Using gh-aw in forks of repositories #18481

Generated by Plan Command for issue #18481

• expires on Feb 28, 2026, 4:18 PM UTC