Fix AI chat re-renders and refactored code (#18585)

This PR: 

- Breaks useAgentChatData into focused effect components (streaming,
fetch,
init, auto-scroll, diff sync)
- Splits message list into non-last (stable) + last (streaming/error) to
prevent full re-renders on each stream chunk
- Adds scroll-to-bottom button and MutationObserver-based auto-scroll on
thread switch
- Lifts loading state from context to atoms
- Adds areEqual to selector
factories

We could improve further but this sets up a robust architecture for
further refactoring.

## Messages flow

The flow of messages loading and streaming is now more solid. 

Everything goes out from `AgentChatAiSdkStreamEffect`, whether loaded
from the DB or streaming directly, and every consumers is using only one
atom `agentChatMessagesComponentFamilyState`

## Data sync effect with callbacks new hook 

See
`packages/twenty-front/src/modules/apollo/hooks/useQueryWithCallbacks.ts`
which allows to fix Apollo v4 migration leftovers and is an
implementation of the pattern we talked about with @charlesBochet

We could refine this pattern in another PR.

# Before



https://github.com/user-attachments/assets/84e7a96f-6790-405d-8a73-2dacbf783be5


# After



https://github.com/user-attachments/assets/4c692e3a-2413-4513-abcc-44d0da311203

Co-authored-by: Charles Bochet <charles@twenty.com>

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

@@ -0,0 +1,47 @@
+import { useProcessUIToolCallMessage } from '@/ai/hooks/useProcessUIToolCallMessage';
+import { agentChatUISessionStartTimeState } from '@/ai/states/agentChatUISessionStartTimeState';
+import { isUIToolCallMessage } from '@/ai/utils/isUIToolCallMessage';
+import { useAtomStateValue } from '@/ui/utilities/state/jotai/hooks/useAtomStateValue';
+import { isNonEmptyString } from '@sniptt/guards';
+import { Temporal } from 'temporal-polyfill';
+import { type ExtendedUIMessage } from 'twenty-shared/ai';
+
+export const useProcessStreamingMessageUpdate = () => {
+  const agentChatUISessionStartTime = useAtomStateValue(
+    agentChatUISessionStartTimeState,
+  );
+
+  const { processUIToolCallMessage } = useProcessUIToolCallMessage();
+
+  const processStreamingMessageUpdate = (
+    streamingMessage: ExtendedUIMessage,
+  ) => {
+    if (agentChatUISessionStartTime === null) {
+      return false;
+    }
+
+    const messageCreatedAt = streamingMessage.metadata?.createdAt;
+
+    if (isNonEmptyString(messageCreatedAt)) {
+      const messageCreatedAtInstant = Temporal.Instant.from(messageCreatedAt);
+
+      const messageIsAfterChatSessionStart =
+        messageCreatedAtInstant.epochNanoseconds >=
+        agentChatUISessionStartTime.epochNanoseconds;
+
+      if (!messageIsAfterChatSessionStart) {
+        return false;
+      }
+    }
+
+    const messageIsUIToolCall = isUIToolCallMessage(streamingMessage);
+
+    if (messageIsUIToolCall) {
+      processUIToolCallMessage(streamingMessage);
+    }
+  };
+
+  return {
+    processStreamingMessageUpdate,
+  };
+};