fix(fleet): filter invalid version strings from UI display (#399)

Treat 'unknown' and '0.0.0-dev' as absent versions in the node
switcher, fleet overview, and capability gate. Remote nodes running
older Docker images that return these fallback values now show a
clean label instead of "vunknown".

frontend/src/components/EditorLayout.tsx

@@ -1350,7 +1350,7 @@ export default function EditorLayout() {
                           node.status === 'offline' ? 'bg-red-500' : 'bg-gray-400'
                           }`} />
                         <span>{node.name}</span>
-                        {meta?.version && (
+                        {meta?.version && meta.version !== 'unknown' && meta.version !== '0.0.0-dev' && (
                           <span className="font-mono text-[10px] tabular-nums text-muted-foreground/60 ml-auto">
                             v{meta.version}
                           </span>