fix: lagging issue in ask AI during message streaming (#16201)

## Changes

### 1. Fixed streaming lag with throttle parameter

**Problem:** The AI chat was experiencing lag during message streaming
because the messages array was being updated too frequently, causing all
messages to re-render too quickly.

**Solution:** Added the `experimental_throttle: 100` parameter to the
`useChat` hook configuration. This throttles message updates during
streaming to prevent excessive re-renders and improve performance.

### 2. Cleaned up useAgentChat hook return values

**Context:** The `useAgentChat` hook primarily returns values from the
underlying `useChat` hook, so there wasn't significant room for
improvement regarding the "umbrella hook" pattern. However, some
unnecessary values were being returned that weren't needed.

**Solution:**
- Removed `input` and `handleInputChange` from the `useAgentChat` hook
return. These weren't needed since input state is already managed
directly via Recoil state (`agentChatInputState`) in components.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Throttle message streaming updates and switch AI chat input management
from context to Recoil; minor scroll behavior tweak.
> 
> - **AI Chat performance**:
> - Add `experimental_throttle: 100` to `useChat` in `useAgentChat` to
reduce re-render frequency during streaming.
> - **State management**:
> - Migrate input handling to Recoil via `agentChatInputState`; remove
`input` and `handleInputChange` from `AgentChatContext` and
`useAgentChat` returns.
> - Update `AIChatTab` and `SendMessageButton` to read/write input from
Recoil and adjust hotkeys/disabled state accordingly.
> - **UX behavior**:
>   - Remove smooth scroll behavior in `useAgentChatScrollToBottom`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
911b341ea1f7c63a4e1e27667da119d9a2960b78. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-front/src/modules/ai/components/internal/SendMessageButton.tsx

@@ -1,8 +1,10 @@
 import { AI_CHAT_INPUT_ID } from '@/ai/constants/AiChatInputId';
 import { useAgentChatContextOrThrow } from '@/ai/hooks/useAgentChatContextOrThrow';
+import { agentChatInputState } from '@/ai/states/agentChatInputState';
 import { type ObjectRecord } from '@/object-record/types/ObjectRecord';
 import { useHotkeysOnFocusedElement } from '@/ui/utilities/hotkey/hooks/useHotkeysOnFocusedElement';
 import { t } from '@lingui/core/macro';
+import { useRecoilValue } from 'recoil';
 import { Key } from 'ts-key-enum';
 import { Button } from 'twenty-ui/input';
 
@@ -11,7 +13,8 @@ export const SendMessageButton = ({
 }: {
   records?: ObjectRecord[];
 }) => {
-  const { handleSendMessage, isLoading, input } = useAgentChatContextOrThrow();
+  const agentChatInput = useRecoilValue(agentChatInputState);
+  const { handleSendMessage, isLoading } = useAgentChatContextOrThrow();
 
   useHotkeysOnFocusedElement({
     keys: [Key.Enter],
@@ -22,7 +25,7 @@ export const SendMessageButton = ({
       }
     },
     focusId: AI_CHAT_INPUT_ID,
-    dependencies: [input, isLoading],
+    dependencies: [agentChatInput, isLoading],
     options: {
       enableOnFormTags: true,
     },
@@ -30,9 +33,9 @@ export const SendMessageButton = ({
 
   return (
     <Button
-      hotkeys={input && !isLoading ? ['⏎'] : undefined}
+      hotkeys={agentChatInput && !isLoading ? ['⏎'] : undefined}
       onClick={() => handleSendMessage(records)}
-      disabled={!input || isLoading}
+      disabled={!agentChatInput || isLoading}
       variant="primary"
       accent="blue"
       size="small"