[DNM] debug author association

[graphaelli]

Test

[github-actions]

This PR adds a debug workflow that will run on every pull request, printing GitHub context variables to help debug author association logic.

Concerns:

1. Should not be merged: The PR title contains "[DNM]" (Do Not Merge), indicating this is temporary test code. If merged, this workflow would add unnecessary CI overhead to every PR.

2. No automatic cleanup: If this is for testing purposes, consider whether the workflow should be removed after debugging is complete.

If this PR is intentionally meant to be merged (contrary to the title), please clarify the use case for having this debug workflow run permanently on all PRs.

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[mergify]

⚠️ The sha of the head commit of this PR conflicts with #17172. Mergify cannot evaluate rules on this PR. ⚠️