Fix cloud-only detection: check for cloud device presence, not exclusivity

The compute-devices endpoint always includes "auto" alongside "cloud",
so checking every() never matched. Use some() to detect cloud sidecar.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/components/Settings.svelte

@@ -48,7 +48,7 @@
 
   let isCloudMode = $derived(remoteMode === "managed" || remoteMode === "byok");
   let isCloudOnly = $derived(
-    computeDevices.length > 0 && computeDevices.every(d => d.id === "cloud")
+    computeDevices.some(d => d.id === "cloud")
   );
 
   // Room creation / join state