PR previews were built + deployed for every apps/packages PR — each one a
journal container + its own database on the flagship, which is a standing
contributor to the disk pressure behind recurring deploy failures and the
2026-07-14 disk-full outage.
Make them opt-in: a preview is built/deployed only when the PR carries the
`preview` label OR a `<!-- preview -->` marker in its description. Gate the
(costly) build-images job, deploy-preview, and — via new labeled/unlabeled
triggers — tear the preview down when the label is pulled, so a de-flagged
PR can't orphan its stack. Main-push / dispatch deploys are unchanged.
Note: the pull_request `paths` filter still applies, so labeling a PR that
touches no apps/packages files won't spin up a preview (nothing to preview).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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