Drive analysis-only chat with analysis.model (falling back to qa.model) so
the running model matches the one the analysis capability configures,
including its vision flag; RAG-bearing chats still run on qa.model.
Give the AG-UI example state-bearing deps and a final STATE_SNAPSHOT so
registered citations reach the client, mirroring the app backend.
Update chat docs: haiku-rag chat uses --capability/-c, and drop the removed
"View state" command-palette entry.
