refactor(playground): extract message removal helper

- move delete-message filtering into conversation message utilities.

- keep the conversation hook focused on action orchestration.

web/default/src/features/playground/hooks/use-playground-conversation.ts

@@ -21,6 +21,7 @@ import {
   appendUserMessagePair,
   applyMessageEdit,
   createRegeneratedMessages,
+  removeMessageByKey,
 } from '../lib'
 import type { Message } from '../types'
 
@@ -96,9 +97,7 @@ export function usePlaygroundConversation({
   const handleDeleteMessage = useCallback(
     (message: Message) => {
       updateMessages((previousMessages) =>
-        previousMessages.filter(
-          (previousMessage) => previousMessage.key !== message.key
-        )
+        removeMessageByKey(previousMessages, message.key)
       )
     },
     [updateMessages]

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

@@ -60,6 +60,13 @@ export function createRegeneratedMessages(
   return [...messages.slice(0, messageIndex), createLoadingAssistantMessage()]
 }
 
+export function removeMessageByKey(
+  messages: Message[],
+  messageKey: string
+): Message[] {
+  return messages.filter((message) => message.key !== messageKey)
+}
+
 export function applyMessageEdit(
   messages: Message[],
   messageKey: string,