refactor(playground): extract completion choice handling

- move non-streaming choice application into the message streaming utilities.
- keep the chat handler focused on request orchestration and message updates.

web/default/src/features/playground/hooks/use-chat-handler.ts

@@ -26,8 +26,8 @@ import {
   updateAssistantMessageWithError,
   updateLastAssistantMessage,
   finalizeMessage,
-  updateCurrentVersionContent,
   parseRequestErrorDetails,
+  applyChatCompletionChoice,
 } from '../lib'
 import type { Message, PlaygroundConfig, ParameterEnabled } from '../types'
 import { useStreamRequest } from './use-stream-request'
@@ -143,16 +143,9 @@ export function useChatHandler({
         }
 
         onMessageUpdate((prev) =>
-          updateLastAssistantMessage(prev, (message) => ({
-            ...finalizeMessage(
-              updateCurrentVersionContent(
-                message,
-                choice.message?.content || ''
-              ),
-              choice.message?.reasoning_content
-            ),
-            status: MESSAGE_STATUS.COMPLETE,
-          }))
+          updateLastAssistantMessage(prev, (message) =>
+            applyChatCompletionChoice(message, choice)
+          )
         )
       } catch (error: unknown) {
         if (abortController.signal.aborted) return

web/default/src/features/playground/lib/message-streaming-utils.ts

@@ -17,7 +17,7 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
 For commercial licensing, please contact support@quantumnous.com
 */
 import { ERROR_MESSAGES, MESSAGE_ROLES, MESSAGE_STATUS } from '../constants'
-import type { Message } from '../types'
+import type { ChatCompletionResponse, Message } from '../types'
 import {
   getCurrentVersion,
   hasMessageContent,
@@ -102,6 +102,21 @@ export function finalizeMessage(
   }
 }
 
+type ChatCompletionChoice = ChatCompletionResponse['choices'][number]
+
+export function applyChatCompletionChoice(
+  message: Message,
+  choice: ChatCompletionChoice
+): Message {
+  return {
+    ...finalizeMessage(
+      updateCurrentVersionContent(message, choice.message?.content || ''),
+      choice.message?.reasoning_content
+    ),
+    status: MESSAGE_STATUS.COMPLETE,
+  }
+}
+
 /**
  * Sanitize messages loaded from storage.
  * Converts stuck loading/streaming messages to stable state.