Shared State Setup - Copilotkit

<Steps> <Step> ### Put shared state in the system prompt and tools

The demo exposes frontend preferences to Claude and gives the agent a tool
for writing notes back into CopilotKit state. Keep the state contract small,
typed, and mirrored by the UI components that read the same values.

<DemoCode file="src/agents/shared_state_read_write_agent.py" region="shared-state-setup" />

</Step> </Steps>