fix: i81n.t and correct button layout issue

1.  **i18n Regression:** A latent bug in `src/routes/(app)/workspace/models/create/+page.svelte` was causing an `i18n.t is not a function` error. This was due to an incorrect call to the `i18n` Svelte store. The fix corrects the call to use the proper auto-subscription syntax (`$i18n.t()`).

2.  **Vertical Button Text:** In `src/lib/components/playground/Chat.svelte`, the "Assistant"/"User" role button's text was displaying vertically. This was caused by a `flex-1` class on its container, which has been removed.

src/lib/components/playground/Chat.svelte

@@ -296,7 +296,7 @@
 					<div
 						class="flex justify-between flex-col sm:flex-row items-start sm:items-center gap-2 mt-2"
 					>
-						<div class="flex-1 shrink-0">
+						<div class="shrink-0">
 							<button
 								type="button"
 								class="px-3.5 py-1.5 text-sm font-medium bg-gray-50 hover:bg-gray-100 text-gray-900 dark:bg-gray-850 dark:hover:bg-gray-800 dark:text-gray-200 transition rounded-lg shrink-0 {($settings?.highContrastMode ??

src/routes/(app)/workspace/models/create/+page.svelte

@@ -16,7 +16,7 @@
 	const onSubmit = async (modelInfo) => {
 		if ($models.find((m) => m.id === modelInfo.id)) {
 			toast.error(
-				i18n.t(
+				$i18n.t(
 					"Error: A model with the ID '{{modelId}}' already exists. Please select a different ID to proceed.",
 					{ modelId: modelInfo.id }
 				)