Relay changes were only testable by deploying prod or a personal stage, so
PR changes to the relay went unexercised until merge. Labeling a same-repo
PR relay:preview now deploys stage pr-<n> behind the relay-preview
environment's reviewer gate. Teardown runs from the default branch on unlabel
or close, with no PR code and no reviewer wait, then sweeps managed tunnels and
their CNAMEs, which Alchemy does not track. A nightly job retries teardown for
closed labeled PRs. Dry-run sweep by default; refuses non-pr-<n> stages.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>