ci: auto-merge the generated contributors PR

[moonD4rk]

Summary

#626 is the first PR the Contributors workflow generated after #625, and it shows the one gap left: 9 checks green, no conflicts, and it still waits for a human to click Squash and merge.

This enables auto-merge on the generated PR via the pr_id output the action already exposes.

• Preconditions hold: the repo has allow_auto_merge: true, and the main ruleset sets required_approving_review_count: 0, so the PR merges the moment the 9 required checks pass.
• Guarded by if: steps.contributors.outputs.pr_id != '' — the action only sets that output when the branch is protected and the README actually changed, so no-op runs skip the step.
• Same app installation token as the action; chore: update contributors list #626 already proved it has pull-requests: write.
• Auto-merge rather than an outright merge keeps the gate intact: the 9 required checks still have to pass, and strict_required_status_checks_policy still forces the branch to be up to date first.
• Values go through env: instead of being interpolated into run:, matching the pattern already used in release.yml.

Beyond removing the manual click, this closes a duplicate-PR failure mode: the action mints a fresh contributors-readme-action-* branch and a brand-new PR on every run with no dedup check, so an unmerged bot PR accumulates a sibling on each subsequent push to main.

Merge order matters — merge #626 first, then this PR. The other way round, this PR's own merge commit triggers Contributors while the README is still stale, opening a second contributors PR alongside #626.

Checklist

• Pull request targets the main branch
• All CI checks pass (lint, test, build)
• I have added tests that prove my fix is effective or that my feature works — N/A, workflow configuration only
• I have added necessary documentation (if appropriate) — N/A
• go.mod directive remains go 1.20 (do not bump)

https://claude.ai/code/session_01X6RUAuQYzireYCp9DTdtSm

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.24%. Comparing base (eed9d99) to head (71c5473).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #627   +/-   ##
=======================================
  Coverage   73.24%   73.24%           
=======================================
  Files          69       69           
  Lines        3184     3184           
=======================================
  Hits         2332     2332           
  Misses        628      628           
  Partials      224      224           

Flag	Coverage Δ
unittests	73.24% <ø> (ø)

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[Copilot]

Pull request overview

This PR updates the Contributors GitHub Actions workflow to automatically enable auto-merge for the PR opened by akhilmhdh/contributors-readme-action when it runs in protected-branch mode, removing the remaining manual “Squash and merge” step once required checks complete.

Changes:

• Assigns an id to the contributors action step so its pr_id output can be referenced.
• Adds a follow-up step that runs gh pr merge ... --squash --auto to enable auto-merge for the generated PR when pr_id is present.

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