chore: add changeset (#5522)

Author: lgrammel

.changeset/green-deers-scream.md

@@ -0,0 +1,8 @@
+---
+'@ai-sdk/ui-utils': major
+'@ai-sdk/react': major
+'@ai-sdk/vue': major
+'ai': major
+---
+
+chore (ui): remove useAssistant hook (**breaking change**)