Verify a published desktop upgrade on another Mac #39

Verify a published desktop upgrade on another Mac: history, Ace Helper and real model work must survive it. This hasn't been verified yet; check the feed or the latest release PR for the current canary version.

Earlier evidence: Desktop builds use the original green Ace icon, with a yellow version for canary. The 0.0.6 canary app and DMG were built from an Ace channel in CI and passed Apple notarization; native Settings, helper startup, channel creation, and human chat passed from /Applications. Credentials are backed up in 1Password and configured in both GitHub release environments. See updates for the release procedure and the earlier checks that resumed real model work after updates. Provider setup waits until agent invocation. Creation and human chat passed without credentials on local, hosted, and packaged runtimes; a retained draft succeeded after adding a real key to the local host. Existing channel history survived the installed-app upgrade.

Tracked by #7. Migrated from TODO.md — Release.