Removes the experimental turn navigator rail beside the session timeline, its Experimental setting, search entry and copy, and the message list `before` query the server and protocol added only for it. The persisted showTurnNavigator key stays as a retired optional preference so stored settings still decode and round-trip.
The server reports its hostname in /api/info. The current server (the
desktop sidecar or the server that served the web app) now shows its
hostname instead of "Local Server" or its address; a custom name still
wins and "This computer" is the fallback when no hostname is known.
Lists omit the current server, and the "This computer" hint appears only
in pickers that choose a server. Remotes on localhost addresses no
longer lose their tags in the new-session project picker.