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/utils/parseInitialBlocknote.ts

@@ -0,0 +1,29 @@
+import type { PartialBlock } from '@blocknote/core';
+import { isArray, isNonEmptyString } from '@sniptt/guards';
+
+export const parseInitialBlocknote = (
+  blocknote?: string | null,
+  logContext?: string,
+): PartialBlock[] | undefined => {
+  if (isNonEmptyString(blocknote) && blocknote !== '{}') {
+    let parsedBody: PartialBlock[] | undefined = undefined;
+
+    // TODO: Remove this once we have removed the old rich text
+    try {
+      parsedBody = JSON.parse(blocknote);
+    } catch {
+      // eslint-disable-next-line no-console
+      console.warn(logContext ?? `Failed to parse blocknote body`);
+      // eslint-disable-next-line no-console
+      console.warn(blocknote);
+    }
+
+    if (!isArray(parsedBody) || parsedBody.length === 0) {
+      return undefined;
+    }
+
+    return parsedBody;
+  }
+
+  return undefined;
+};