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/routes/(chat)/+page.svelte

@@ -3,7 +3,6 @@
 	import { chatStore } from '$lib/stores/chat.svelte';
 	import { conversationsStore, isConversationsInitialized } from '$lib/stores/conversations.svelte';
 	import { modelsStore, modelOptions } from '$lib/stores/models.svelte';
-	import { isRouterMode } from '$lib/stores/server.svelte';
 	import { onMount } from 'svelte';
 	import { page } from '$app/state';
 	import { replaceState } from '$app/navigation';
@@ -72,23 +71,13 @@
 		conversationsStore.clearActiveConversation();
 		chatStore.clearUIState();
 
-		if (
-			isRouterMode() &&
-			modelsStore.selectedModelName &&
-			!modelsStore.isModelLoaded(modelsStore.selectedModelName)
-		) {
-			modelsStore.clearSelection();
+		await modelsStore.fetch();
 
-			const first = modelOptions().find((m) => modelsStore.loadedModelIds.includes(m.model));
-			if (first) {
-				await modelsStore.selectModelById(first.id);
-			}
-		}
-
-		// Handle URL params only if we have ?q= or ?model= or ?new_chat=true
 		if (qParam !== null || modelParam !== null || newChatParam === 'true') {
 			await handleUrlParams();
 		}
+
+		await modelsStore.ensureFirstModelSelected();
 	});
 </script>