5.16.0

(feat): Implement transparent SSE stream auto-reconnection for resumable: true endpoints, bringing the Python SDK to parity with TypeScript and Go. When a resumable stream ends prematurely, EventSource now re-issues the original request with a Last-Event-ID header and resumes from the last dispatched event id (never a parsed-but-undispatched id, avoiding silent event loss). Reconnection is gated on a configured stream terminator, honors stream_reconnection_enabled and max_stream_reconnection_attempts (with reset-on-progress), backs off 1s by default (or the server retry: value, clamped to 30s), guards against empty reconnect bodies, and remains cancellable during the backoff delay. Supported for both sync and async clients.