Fix update_reaction job failure when agent output artifact is missing

[Copilot]

Problem

The update_reaction job fails when the agent doesn't produce an output artifact, as seen in workflow run #18603329251. The failure occurs because:

1. The artifact download step fails (expected, using continue-on-error: true)
2. When the download fails, the directory /tmp/gh-aw/safe-outputs/ is never created by the actions/download-artifact action
3. The subsequent find /tmp/gh-aw/safe-outputs/ -type f -print command fails with exit code 1

##[error]Unable to download artifact(s): Artifact not found for name: agent_output.json
find: '/tmp/gh-aw/safe-outputs/': No such file or directory
##[error]Process completed with exit code 1.

Solution

Modified the buildAgentOutputDownloadSteps() function in pkg/workflow/safe_output_helpers.go to create the directory before attempting to list its contents:

- name: Setup agent output environment variable
  run: |
    mkdir -p /tmp/gh-aw/safe-outputs/
    find /tmp/gh-aw/safe-outputs/ -type f -print
    echo "GITHUB_AW_AGENT_OUTPUT=/tmp/gh-aw/safe-outputs/agent_output.json" >> $GITHUB_ENV

This ensures the directory exists even when the artifact download fails, allowing the job to continue gracefully.

Impact

This fix applies to all safe output jobs that download agent output artifacts:

• add_comment job
• missing_tool job
• update_reaction job

These jobs will now handle the case where the agent doesn't produce output artifacts without failing.

Testing

• Added TestBuildAgentOutputDownloadSteps to verify directory creation occurs before the find command
• All existing tests pass
• Recompiled all 64 workflows successfully
• Verified the fix appears in generated workflow files

Original prompt

The javascript for the "update_reaction" job needs to handle the case where the agent output artifact was not created and the folder is not present.

See error in update_reaction job in https://github.com/githubnext/gh-aw/actions/runs/18603329251/job/53047201050

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