process: a failed read of open issues never files a duplicate (#700 r1)

CODE-REVIEW-700-r1 Medium: `gh issue list … || true` turned a failed read
into an empty answer, and the step went on to gh issue create — a second
[workflow-sync] issue next to the open one on every network or rate-limit
failure. A failed read now warns and exits 0; creating stays reserved for
«read succeeded, nothing open».

Mutant workflow-sync-issue-duplicated-on-read-failure.

Issue: #700
User-Visible: no
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018qZfe7YS4rqEMKoVeS3GKd

.github/workflows/validate.yml

@@ -158,8 +158,13 @@ jobs:
           RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
         run: |
           marker="[workflow-sync]"
-          existing=$(gh issue list --repo "$REPO" --state open --search "\"$marker\" in:title" \
-            --json number,title --jq '[.[] | select(.title | startswith("[workflow-sync]"))][0].number // empty' || true)
+          # Список не прочитан — нового issue нет: иначе сбой сети или
+          # рейт-лимит плодил бы дубликат к уже открытому (r1 #700).
+          if ! existing=$(gh issue list --repo "$REPO" --state open --search "\"$marker\" in:title" \
+            --json number,title --jq '[.[] | select(.title | startswith("[workflow-sync]"))][0].number // empty'); then
+            echo "::warning::открытые issue не прочитаны — новое не заводится, чтобы не завести дубликат"
+            exit 0
+          fi
           if [ -n "$existing" ]; then
             gh issue comment "$existing" --repo "$REPO" --body "Расхождение повторилось: $RUN_URL" \
               || echo "::warning::комментарий в #$existing не оставлен"