apps/web/src/components/chat/ChatComposer.tsx             |  90 +++++++++++++++++------
 apps/web/src/components/chat/composerMentionDrag.test.ts  | 123 ++++++++++++++++++++++++++++++++
 apps/web/src/components/chat/composerMentionDrag.ts       |  98 +++++++++++++++++++++++++
 apps/web/src/components/files/FileBrowserPanel.tsx        |  44 ++++++++++++
 apps/web/src/components/files/fileTreeDragMention.test.ts | 112 +++++++++++++++++++++++++++++
 apps/web/src/components/files/fileTreeDragMention.ts      |  95 ++++++++++++++++++++++++
 6 files changed, 542 insertions(+), 20 deletions(-)