assistant-ui Update

Always verifies against npm ground truth and GitHub commits.

References

• ./references/ai-sdk-v6.md -- AI SDK v4/v5 → v6 migration (complete guide)
• ./references/assistant-ui.md -- assistant-ui version migrations
• ./references/breaking-changes.md -- Quick reference table

Phase 1: Detect Versions

Get Ground Truth

npm ls @assistant-ui/react @assistant-ui/react-ai-sdk ai @ai-sdk/react 2>/dev/null