New Chat scene at the Chat top-bar tab. Threads and messages are stored
as flow docs (kind=definition, source_context=EA2_CHAT_THREAD / _MSG)
linked by defines edges with role=next — same proven contract as wizard
steps. Persona directory lets the signed-in operator open a thread with
the CEO / HR / IT personas.
- src/lib/chatApi.ts: listThreads / createThread / listMessages / sendMessage
- src/scenes/Chat.tsx: sidebar (threads + new-thread picker) + main pane
(header, bubbles, composer with Enter-to-send / Shift-Enter newline)
- src/index.css: chat-scene grid + bubble + composer styles
- src/App.tsx: Chat tab + scene route
