When a GitHub issue with a github_post_links row is closed with state_reason=completed, flip the linked Hollahoop post to the project Shipped status. Append a "Closed by PR title" footer to post body when the closing PR is detected. Per-project toggle for "Reopen post if issue is reopened" (default off — engineering teams reopen issues for QA, not for regression).

Implements the issues.closed and pull_request.closed webhook handlers. Idempotent via webhook_events.delivery_id. Does NOT mirror comments, does NOT sync issue body — strictly status signal only.