ui : show the assistant model selector for external backends

Assisted-by: pi:llama.cpp/DeepSeek-V4.1-Flash

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessage/ChatMessageAssistant/ChatMessageAssistant.svelte

@@ -166,7 +166,6 @@
 				<ChatMessageAssistantModel
 					{displayedModel}
 					isLoading={chatStore.isLoading}
-					{isRouter}
 					{onRegenerate}
 				/>
 

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessage/ChatMessageAssistant/ChatMessageAssistantModel.svelte

@@ -1,17 +1,21 @@
 <script lang="ts">
 	import { ModelBadge, ModelsSelectorDropdown } from '$lib/components/app';
 	import { ServerModelStatus } from '$lib/enums';
-	import { modelsStore } from '$lib/stores';
+	import { modelsStore, serverStore } from '$lib/stores';
 	import { copyToClipboard } from '$lib/utils';
 
 	interface Props {
 		displayedModel: string | null;
-		isRouter: boolean;
 		isLoading: boolean;
 		onRegenerate: (modelOverride?: string) => void;
 	}
 
-	let { displayedModel, isLoading, isRouter, onRegenerate }: Props = $props();
+	let { displayedModel, isLoading, onRegenerate }: Props = $props();
+
+	// same selectability rule as the form selector: router mode, or any backend
+	// that exposes a selectable model list
+	let isSelectable = $derived(serverStore.isRouterMode || !serverStore.capabilities.props);
+	let canLoadModels = $derived(serverStore.capabilities.loadUnload);
 
 	let pendingModel = $state<string | null>(null);
 
@@ -20,14 +24,15 @@
 	}
 </script>
 
-{#if isRouter}
+{#if isSelectable}
 	<ModelsSelectorDropdown
 		currentModel={pendingModel ?? displayedModel}
 		disabled={isLoading}
 		onModelChange={async (modelId: string, modelName: string) => {
 			const status = modelsStore.getModelStatus(modelId);
 
-			if (status !== ServerModelStatus.LOADED) {
+			// external backends load the model implicitly on the request
+			if (canLoadModels && status !== ServerModelStatus.LOADED) {
 				pendingModel = modelId;
 
 				try {