feat(app): unified provider snapshot, resilient model selector, and UX polish

- Model selector is no longer disabled while providers load; opens
  immediately and streams available providers as they arrive
- Selecting a non-default provider on mobile now works correctly
- Provider icon added to model trigger in mobile preferences sheet
- Thinking icon (brain) added to thinking trigger in mobile preferences
- Model descriptions for OpenCode/Pi shown inline next to model name
  instead of in a tooltip
- Running agents and draft screen share a single provider/model cache,
  eliminating duplicate network requests
- Provider data is prefetched when entering a workspace so the model
  selector is instant on first open

packages/app/src/screens/workspace/workspace-screen.tsx

@@ -70,6 +70,7 @@ import {
   workspaceTabTargetsEqual,
 } from "@/utils/workspace-tab-identity";
 import { useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-runtime";
+import { prefetchProvidersSnapshot } from "@/hooks/use-providers-snapshot";
 import { useWorkspaceTerminalSessionRetention } from "@/terminal/hooks/use-workspace-terminal-session-retention";
 import {
   checkoutStatusQueryKey,
@@ -608,6 +609,16 @@ function WorkspaceScreenContent({ serverId, workspaceId }: WorkspaceScreenProps)
   const client = useHostRuntimeClient(normalizedServerId);
   const isConnected = useHostRuntimeIsConnected(normalizedServerId);
 
+  useEffect(() => {
+    if (!client || !isConnected || !normalizedServerId) {
+      return;
+    }
+    const session = useSessionStore.getState().sessions[normalizedServerId];
+    if (session?.serverInfo?.features?.providersSnapshot) {
+      prefetchProvidersSnapshot(normalizedServerId, client);
+    }
+  }, [client, isConnected, normalizedServerId]);
+
   const workspaceAgentVisibility = useStoreWithEqualityFn(
     useSessionStore,
     (state) =>