check_for_updates now fetches the manifest as raw JSON and runs
trust::verify_detached before parsing: a tampered or wrong-signer
signature rejects the mirror outright, and unsigned manifests are
offered for MANUAL apply only — the 3 AM auto-apply scheduler refuses
them, closing the unattended remote-root hole (§A of the 1.8.0
hardening plan). UpdateState gains manifest_signed so the UI can
surface authenticity.
Publisher side: create-release.sh signs the manifest during the
release (ceremony, mnemonic via TTY/env only), publish-release-assets
hard-refuses to ship an unsigned manifest (grep + new 'ceremony
verify' cryptographic gate), and scripts/sign-manifest.sh covers
re-signing outside a release run.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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