The Preview update channel was effectively dead: its only build trigger was a
manual workflow_dispatch, so "preview = main" was never enforced — the live
preview manifest was stuck at 0.3.5-41 (June 7) while main moved to 0.3.7.
It also shipped two latent hazards: the `preview` GitHub release had drifted to
isPrerelease=false (a non-prerelease `preview` is eligible to become GitHub's
"Latest" — the exact URL the *stable* updater reads, so it could hijack the
Stable channel), and its updater manifest dropped darwin-x86_64 (Intel-Mac
preview users silently got no updates — a cross-platform-parity breach).
Changes (release.yml):
- Add a nightly `schedule` (07:00 UTC) that rebuilds the rolling `preview`
prerelease from main. A new `preview-gate` job no-ops the 4-platform matrix
on nights when main didn't move, so idle days cost only a ~30s gate job.
- Centralize the preview-vs-stable decision in `preview-gate.outputs.is_preview`
(schedule OR workflow_dispatch+publish_preview), consumed by the stamp step,
tauri-action, and preview-notes — replacing the repeated inline conditions.
- Harden the prerelease flag: preview-notes' `gh release edit` now re-asserts
`--prerelease` every run, and a new post-publish step fails the run if the
preview release isn't a prerelease or its manifest is missing any platform
stable ships (catches the Intel-Mac regression in CI).
Docs (docs-sync): update docs/update-channels.md — previews are no longer
"manual / no scheduled spend"; they build nightly from main (+ on demand).
The live `preview` release was re-flagged prerelease out-of-band to close the
hazard immediately; this makes it recurrence-proof.
Co-authored-by: mergetest <test@local>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
