prefix property
The namespace every key of this store is written under.
Another app embedding this package — the OmnyServer dashboard, say — is
very likely served from the same origin as this one (one Hub can host
both), and localStorage is per-origin. Sharing the namespace would mean
sharing, and clobbering, each other's theme, Hub, token and terminal
preferences. Give each app its own prefix.
Implementation
final String prefix;