Recovery command for failed post-release sync PR

[hdamker]

Problem description

When the post-release sync PR creation fails after a successful publish (e.g., due to a transient GitHub API error), there is no automated way to retry. The Release Issue remains open with a warning about the sync anomaly, but the only recovery path is manual: create the branch, copy CHANGELOG and README content from the release tag, and create the PR by hand.

Possible evolution

Add a /create-sync-pr <tag> slash command that triggers the sync PR job for an already-published release. The command would:

1. Verify the release tag exists and is published
2. Create the tmp/sync-main/<tag> branch from the release tag
3. Copy CHANGELOG and README release info block to the branch
4. Create the PR targeting main

Alternative solution

Document the manual recovery steps as a runbook. The failure is rare (observed once across all E2E testing and production releases), so the manual workaround may be sufficient.

Additional context

The sync PR logic already exists in the create-sync-pr job of the reusable workflow. The recovery command would reuse this logic, triggered independently of the publish flow.