Fix the Turbopack dev server's route-change announcements. Establish the initial App Router route set without reporting it as a change. Thereafter, when routes are added or removed, announce exactly the routes that changed, using public URL route names (for example, `/blog`) rather than App Router entrypoint names (such as `/blog/page`). Existing routes must not be reannounced as added or removed, because every extra announcement forces connected tabs to refetch. A single route addition or removal should therefore produce only its corresponding announcement and no unrelated messages.