Chat endpoint that streams Claude responses (and tool calls) to the client using Server-Sent Events (SSE).

Supports both Auth0 JWT authentication (Authorization: Bearer) and API key authentication (X-API-Key header) for service-to-service integrations.

Each SSE event has the following format:

event: <text|tool_use|tool_result>

data: <JSON-encoded payload>

Where the payload structure corresponds to the event type, e.g. {"text": "Hello"} for text, {"name": "get_weather", "args": {...}} for tool_use, and {"name": "get_weather", "content": "72F and sunny"} for tool_result.