fix: prevent ext-contribution label on release and github-actions PRs

The check-author job added the ext-contribution label to PR #9311
(release: 2026-07-06). Its opened event fired before the auto-pr label was
applied, so the existing !contains(labels, 'auto-pr') guard saw the empty
label snapshot and passed; since github-actions[bot] is not a team dev, the
label was added.

Guard on the head ref and author login instead - both are present in the
opened payload immediately, so they do not race asynchronous label creation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: mikhail-dcl

.github/workflows/claude-pr-review.yml

@@ -13,6 +13,8 @@ jobs:
     if: |
       github.event_name == 'pull_request' &&
       github.event.pull_request.draft == false &&
+      github.event.pull_request.user.login != 'github-actions[bot]' &&
+      !startsWith(github.head_ref, 'release/') &&
       !contains(github.event.pull_request.labels.*.name, 'no review') &&
       !contains(github.event.pull_request.labels.*.name, 'auto-pr') &&
       (github.event.action != 'labeled' || github.event.label.name == 'ext-contribution')