Turn on `.strictMemorySafety()` for the `Byre` target in `mac/Package.swift` and resolve what it flags (`@unchecked Sendable` on `Re`, `MainActor.assumeIsolated` in the key and click monitors, and anything else), so `swift build` is warning-free with it on.
- macOS client signing and SwiftData with iCloud sync
Sign `byre.app` with the paid developer team (provisioning profile, iCloud and CloudKit entitlements) in `mac/bundle.sh`, and move the app's persisted state (the `byre.server` origin, drafts, last visits) from `UserDefaults` to SwiftData with CloudKit sync, so the server address follows the user to every Mac.
Side by side with the web client on the same server, window size and appearance, using disposable tasks: every tab, switcher, Inbox choice types, merge/discard dialogs, light/dark, narrow windows. Document build, install and storage in `docs/operations.md`.