fix(ai-chat): sort message parts by orderIndex on reload (#22629)

## Problem

When an AI chat conversation is reloaded from the DB (page refresh or
initial load), message parts are returned without guaranteed ordering.
The renderer groups reasoning/thinking steps only when they are
**contiguous** — so if `reasoning` parts land after the `text` part,
thinking blocks appear below the final answer, and can appear duplicated
or split.

This only surfaces with reasoning models (OpenRouter, etc.) because
those produce multiple reasoning/tool/text parts per message, making
ordering observable. Simple text-only messages aren't affected.

## Root cause

`AgentChatService.getMessagesForThread()` fetches `parts` via a TypeORM
relation with no ORDER BY on `orderIndex`. The DB can return parts in
any order.

`mapDBMessagesToUIMessages()` then calls `dbMessage.parts.map(...)`
directly, without sorting.

A parallel server-side utility (`mapDBPartsToUIMessageParts.ts`) already
sorts by `orderIndex` — this fix makes the frontend fetch path
consistent with it.

## Fix

Sort parts by `orderIndex` before mapping to UI parts in
`mapDBMessagesToUIMessages.ts`.

```ts
parts: [...dbMessage.parts]
  .sort((a, b) => a.orderIndex - b.orderIndex)
  .map(mapDBPartToUIMessagePart),
```

`orderIndex` is already included in `GetChatMessagesDocument` — no
schema or query changes needed.

## Test

1. Open Ask AI with a reasoning model (e.g. via OpenRouter).
2. Run a prompt that produces thinking steps.
3. Hard-refresh the page.
4. Thinking blocks should appear collapsed above the final answer, not
below it.

Closes #22386

<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/22629?utm_source=github"
target="_blank" rel="noopener noreferrer"
data-no-image-dialog="true"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"><source
media="(prefers-color-scheme: light)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-light.svg"><img
alt="Review in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"></picture></a>
<!-- End of auto-generated description by cubic. -->

packages/twenty-front/src/modules/ai/utils/mapDBMessagesToUIMessages.ts

@@ -9,7 +9,9 @@ export const mapDBMessagesToUIMessages = (
     id: dbMessage.id,
     role: dbMessage.role as ExtendedUIMessage['role'],
     status: dbMessage.status as 'queued' | 'sent',
-    parts: dbMessage.parts.map(mapDBPartToUIMessagePart),
+    parts: [...dbMessage.parts]
+      .sort((a, b) => a.orderIndex - b.orderIndex)
+      .map(mapDBPartToUIMessagePart),
     metadata: {
       createdAt: dbMessage.createdAt,
     },