Add @mention support in AI Chat input (#17943)

## Summary
- Add `@mention` support to the AI Chat text input by replacing the
plain textarea with a minimal Tiptap editor and building a shared
`mention` module with reusable Tiptap extensions (`MentionTag`,
`MentionSuggestion`), search hook (`useMentionSearch`), and suggestion
menu — all shared with the existing BlockNote-based Notes mentions to
avoid code duplication
- Mentions are serialized as
`[[record:objectName:recordId:displayName]]` markdown (the format
already understood by the backend and rendered in chat messages), and
displayed using the existing `RecordLink` chip component for visual
consistency
- Fix images in chat messages overflowing their container by
constraining to `max-width: 100%`
- Fix web_search tool display showing literal `{query}` instead of the
actual query (ICU single-quote escaping issue in Lingui `t` tagged
templates)

## Test plan
- [ ] Open AI Chat, type `@` and verify the suggestion menu appears with
searchable records
- [ ] Select a mention from the dropdown (via click or keyboard
Enter/ArrowUp/Down) and verify the record chip renders inline
- [ ] Send a message containing a mention and verify it appears
correctly in the conversation as a clickable `RecordLink`
- [ ] Verify Enter sends the message when the suggestion menu is closed,
and selects a mention when the menu is open
- [ ] Verify images in AI chat responses are constrained to the
container width
- [ ] Verify the web_search tool step shows the actual search query
(e.g. "Searched the web for Salesforce") instead of `{query}`
- [ ] Verify Notes @mentions still work as before


Made with [Cursor](https://cursor.com)

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/twenty-front/src/modules/blocknote-editor/components/CustomAddBlockItem.tsx

@@ -0,0 +1,45 @@
+import { type BLOCK_SCHEMA } from '@/blocknote-editor/blocks/Schema';
+
+import { useComponentsContext } from '@blocknote/react';
+
+type CustomAddBlockItemProps = {
+  editor: typeof BLOCK_SCHEMA.BlockNoteEditor;
+  children: React.ReactNode; // Adding the children prop
+};
+
+type ContentItem = {
+  type: string;
+  text: string;
+  styles: any;
+};
+export const CustomAddBlockItem = ({
+  editor,
+  children,
+}: CustomAddBlockItemProps) => {
+  const Components = useComponentsContext();
+
+  if (!Components) {
+    return null;
+  }
+
+  const handleClick = () => {
+    const blockIdentifier = editor.getTextCursorPosition().block;
+    const currentBlockContent = blockIdentifier?.content as
+      | Array<ContentItem>
+      | undefined;
+
+    const [firstElement] = currentBlockContent || [];
+
+    if (firstElement === undefined) {
+      editor.openSuggestionMenu('/');
+    } else {
+      editor.openSuggestionMenu('/');
+      editor.sideMenu.unfreezeMenu();
+    }
+  };
+  return (
+    <Components.Generic.Menu.Item onClick={handleClick}>
+      {children}
+    </Components.Generic.Menu.Item>
+  );
+};