Fix stray bracket after AI chat chips (#23798)

Chips in the AI chat sometimes rendered with a leftover `]` after them.

The reference marker is bracket-asymmetric: it opens with `[[` and
closes with `[[/kind]]`, so a complete reference holds four `[` and only
two `]`. The model balances that by writing `…[[/object]]]`, and the
parser ended the match exactly at the close tag, leaving the extra
bracket as prose next to the chip.

The parser now absorbs up to as many surplus `]` as the reference opened
with, and accepts an opener with extra `[` so an over-wrapped marker
doesn't leak one either. The system prompt also tells the model the
marker is complete as written.

<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/23798?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/getChatReferenceStartFromMatch.ts

@@ -1,6 +1,8 @@
 import { type ChatReferenceStart } from '@/ai/types/ChatReferenceStart';
 import { isDefined } from 'twenty-shared/utils';
 
+const OPEN_BRACKETS_REGEX = /^\[+/;
+
 export const getChatReferenceStartFromMatch = (
   match: RegExpExecArray,
 ): ChatReferenceStart => {
@@ -12,7 +14,15 @@ export const getChatReferenceStartFromMatch = (
     recordId,
   } = match.groups ?? {};
 
-  const position = { index: match.index, prefixLength: match[0].length };
+  const openBracketsMatch = OPEN_BRACKETS_REGEX.exec(match[0]);
+
+  const position = {
+    index: match.index,
+    prefixLength: match[0].length,
+    openBracketLength: isDefined(openBracketsMatch)
+      ? openBracketsMatch[0].length
+      : 0,
+  };
 
   if (isDefined(objectNameSingular)) {
     return { ...position, identity: { kind: 'object', objectNameSingular } };