Add a bounded relation graph and knowledge journeys.

CONTENT-WP-0004 keeps outgoing and incoming labels apart, limits the graph to two hops, and stores focus and detail in the URL.

Assistant: grok
Assistant-Session: 01a1531b-6698-7732-8587-f28ea604bcdf

ui/components/SiteHeader.tsx

@@ -22,6 +22,7 @@ export function SiteHeader({ dataspaces }: { dataspaces: DataspaceNav[] }) {
         {active ? (
           <nav aria-label="Primary" className="flex min-w-0 items-center gap-4 overflow-x-auto text-sm">
             <a href={`/${active.id}/`} className="shrink-0 text-foreground">{active.title}</a>
+            <a href={`/${active.id}/graph/`} className="shrink-0 text-muted hover:text-foreground">Graph</a>
             {active.kinds.map((kind) => (
               <a key={kind.id} href={kind.href} className="shrink-0 text-muted hover:text-foreground">
                 {kind.plural}