pyrefly rejected flask.stream_with_context called with a generator
(constrained AnyStr overload — "no-matching-overload"), failing the
Python type-check CI. Switch the streaming endpoint to the repo's
established SSE helper compact_generate_response (which wraps
_stream_with_request_context), so it type-checks and still preserves
request context during iteration.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>