ui: Refactor models store, MCP service, and gate logs behind VITE_DEBUG (#23236)

* refactor: Scope console logs to `DEV` + `VITE_DEBUG` env vars

* refactor: skip MCP proxy probe when no server requires it

* refactor: suppress expected disconnect errors during MCP client shutdown

* refactor: Deduplicate requests

* refactor: deduplicate model fetching across ROUTER and MODEL modes

* refactor: Clean up models logic

* chore: Add `.env.example` file

* refactor: replace client-side CORS proxy probe with server status flag

* refactor: Post-review fixes

* test: add vitest client setup with API fetch mocks

tools/ui/src/lib/components/app/chat/ChatForm/ChatFormActions/ChatFormActionModels.svelte

@@ -7,7 +7,6 @@
 	import { activeMessages } from '$lib/stores/conversations.svelte';
 
 	interface Props {
-		currentModel?: string;
 		disabled?: boolean;
 		forceForegroundText?: boolean;
 		hasAudioModality?: boolean;
@@ -20,7 +19,6 @@
 	}
 
 	let {
-		currentModel,
 		disabled = false,
 		forceForegroundText = false,
 		hasAudioModality = $bindable(false),
@@ -41,14 +39,28 @@
 
 	let lastSyncedConversationModel: string | null = null;
 
+	let selectorModel = $derived(conversationModel ?? modelsStore.selectedModelName ?? null);
+
 	$effect(() => {
 		if (conversationModel && conversationModel !== lastSyncedConversationModel) {
-			lastSyncedConversationModel = conversationModel;
+			if (modelOptions().some((m) => m.model === conversationModel)) {
+				modelsStore.selectedModelName = conversationModel;
+				modelsStore.selectModelByName(conversationModel);
+			} else {
+				modelsStore.selectedModelName = null;
+				modelsStore.clearSelection();
+			}
 
-			modelsStore.selectModelByName(conversationModel);
-		} else if (isRouter && !modelsStore.selectedModelId && modelsStore.loadedModelIds.length > 0) {
+			lastSyncedConversationModel = conversationModel;
+		} else if (
+			isRouter &&
+			!modelsStore.selectedModelId &&
+			modelsStore.loadedModelIds.length > 0 &&
+			activeMessages().length > 0 &&
+			!conversationModel
+		) {
 			lastSyncedConversationModel = null;
-			// auto-select the first loaded model only when nothing is selected yet
+
 			const first = modelOptions().find((m) => modelsStore.loadedModelIds.includes(m.model));
 
 			if (first) modelsStore.selectModelById(first.id);
@@ -151,7 +163,7 @@
 	<ModelsSelectorSheet
 		disabled={disabled || isOffline}
 		bind:this={selectorModelRef}
-		{currentModel}
+		currentModel={selectorModel}
 		{forceForegroundText}
 		{useGlobalSelection}
 	/>
@@ -159,7 +171,7 @@
 	<ModelsSelectorDropdown
 		disabled={disabled || isOffline}
 		bind:this={selectorModelRef}
-		{currentModel}
+		currentModel={selectorModel}
 		{forceForegroundText}
 		{useGlobalSelection}
 	/>

tools/ui/src/lib/components/app/chat/ChatForm/ChatFormPickers/ChatFormPickerMcpPrompts/ChatFormPickerMcpPrompts.svelte

@@ -162,7 +162,7 @@
 			return;
 		}
 
-		if (import.meta.env.DEV) {
+		if (import.meta.env.DEV && import.meta.env.VITE_DEBUG) {
 			console.log('[ChatFormPickerMcpPrompts] Fetching completions for:', {
 				serverName: selectedPrompt.serverName,
 				promptName: selectedPrompt.name,
@@ -181,7 +181,7 @@
 				value
 			);
 
-			if (import.meta.env.DEV) {
+			if (import.meta.env.DEV && import.meta.env.VITE_DEBUG) {
 				console.log('[ChatFormPickerMcpPrompts] Autocomplete result:', {
 					argName,
 					value,