feat(config): add review.auto_merge_summary read-only knob (#2051) - #3829

GitHub PR search returned no authored pull requests for user 'Lang-bt' (warning: 'GitHub PR search returned no authored pull requests or was unavailable.'). The evidence packet contains zero candidate, hydrated, or omitted PRs, and activity metrics show totalEvents=0, prCount=0, and no repository interactions. Without patch-level code to adversarially review, no execution paths, dependencies, network calls, lifecycle hooks, or permission changes can be assessed. Per guidance, when evidence is insufficient no safe or caution verdict can be substantiated, and the contributor must not be marked safe merely because data is missing. Verdict is inconclusive pending available hydrated patches.