Run agentscan if first-contribution left a comment - #32338

PR summary

This PR adds an additional step to the "PR Greetings" workflow: if first-contribution leaves a comment, we then run agentscan and potentially add a label.

What is agentscan?

AgentScan is a website, GitHub action, and GitHub app that uses identity to figure out automation patterns. See https://agentscan.tools/adopters for a list of other projects using it (notably: node.js).

I found the website a few days ago and have been reviewing previously-closed PRs with it. It seems to do a very good job of detecting automated activity. The website provides graphs of authors' recent history.

Approach

My first idea was to make a new workflow that would run when the first-contributor label was applied. Based on yesterday's meeting comments regarding the PR Template checker, I'm not sure if this will work.

Instead, I check the comment-url output of the first-contribution action. This should be an empty string if no comment was left. This adds an additional contents: read permission to the job that first-contribution doesn't need. I'm not sure if there is a better way to isolate permissions.

Only labels are added to help triage. While agentscan has other features, I didn't want it to automatically close PRs or make comments.

This is my first time using GitHub workflows, I probably made mistakes. Please scrutinize.

Open questions for discussion:

• Do we want to do this at all?
• Should we only add a label for "automated" and not "mixed"?
• Should we change the label names?

Follow-up Work

If this is approved, we will need to add the corresponding GitHub labels prior to merging.

AI Disclosure

• I used AI to help me figure out the exact YAML syntax to use.
• All of the individual settings were chosen by me after reading through the agentscan documentation.

PR quality check

• Use an expressive title, e.g. "Fix title font property precedence"
• [N/A] New and changed code is tested I could not figure out a good way to test this
• [N/A] Plotting related features are demonstrated in an example
• [N/A] New features and API changes have release notes
• [N/A] Documentation complies with general and docstring guidelines