fix(ask-ai): resolve stream subscription race condition on new thread… (#21916)

## Description
Resolves a race condition in the Ask AI feature where the first
assistant reply in a newly created thread does not stream into the UI
and only appears after sending a second message.

### What's Changed
- **Immediate Thread Subscription:** Updated `useAgentChat.ts` to
immediately set `currentAiChatThread` to the newly generated `threadId`
instead of deferring it until after the `SEND_CHAT_MESSAGE` mutation
finishes.
- **The Bug:** Previously, the backend worker processed the AI chat job
so quickly that the stream completed and fired the `message-persisted`
event *before* the frontend established the SSE subscription.
- **The Fix:** By setting the thread ID immediately, the
`useAgentChatSubscription` hook now properly connects and listens to the
SSE stream before the backend begins emitting chunks, guaranteeing the
first message streams seamlessly.

### How to Test
1. Open the Ask AI panel and start a completely new thread.
2. Send an initial message (e.g., "Hello!").
3. Observe that the AI's response successfully streams into the chat
without needing a workaround or page refresh.

Closes #21694

---------

Co-authored-by: Etienne <45695613+etiennejouan@users.noreply.github.com>

packages/twenty-front/src/modules/ai/hooks/useAgentChat.ts

@@ -1,7 +1,7 @@
 import { CombinedGraphQLErrors } from '@apollo/client/errors';
 import { useApolloClient } from '@apollo/client/react';
 import { useStore } from 'jotai';
-import { useCallback, useState } from 'react';
+import { useCallback } from 'react';
 import { type ExtendedUIMessage } from 'twenty-shared/ai';
 import { isDefined, isValidUuid } from 'twenty-shared/utils';
 import { v4 } from 'uuid';
@@ -44,8 +44,6 @@ export const useAgentChat = (
   const setCurrentAiChatThread = useSetAtomState(currentAiChatThreadState);
   const store = useStore();
 
-  const [, setPendingThreadIdAfterFirstSend] = useState<string | null>(null);
-
   const setAgentChatUploadedFiles = useSetAtomState(
     agentChatUploadedFilesState,
   );
@@ -87,7 +85,7 @@ export const useAgentChat = (
     }
 
     if (draftKey === AGENT_CHAT_NEW_THREAD_DRAFT_KEY) {
-      setPendingThreadIdAfterFirstSend(threadId);
+      setCurrentAiChatThread(threadId);
     }
 
     setAgentChatInput('');
@@ -184,14 +182,6 @@ export const useAgentChat = (
       }
 
       dispatchBrowserEvent(AGENT_CHAT_REFETCH_MESSAGES_EVENT_NAME);
-
-      setPendingThreadIdAfterFirstSend((pendingId) => {
-        if (isDefined(pendingId)) {
-          setCurrentAiChatThread(pendingId);
-        }
-
-        return null;
-      });
     } catch (error) {
       const restoredDraftKey =
         draftKey === AGENT_CHAT_NEW_THREAD_DRAFT_KEY ? threadId : draftKey;
@@ -225,12 +215,6 @@ export const useAgentChat = (
       dispatchBrowserEvent(AGENT_CHAT_RESTORE_EDITOR_CONTENT_EVENT_NAME, {
         content: contentToSend,
       });
-
-      if (draftKey === AGENT_CHAT_NEW_THREAD_DRAFT_KEY) {
-        setCurrentAiChatThread(threadId);
-      }
-
-      setPendingThreadIdAfterFirstSend(null);
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [