Replace bufio.Scanner with bufio.NewReaderSize + ReadBytes('\n') across all
SSE read paths to preserve long single-line data (e.g. write_file content).
Add quasi_status and auto_continue handling as direct path-based patches in
both Go continue observer and Node vercel_stream_impl, mirroring existing
batch-patch logic. Add 2MiB+ line throughput tests at every SSE layer.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
