Replace newline-delimited text protocol with length-prefixed blobs
for all response data (send_ok_string, send_ok_raw). The OCaml side
sends (ok-len N)\n followed by exactly N raw bytes + \n. Python reads
the length, then readexactly(N).
This eliminates all pipe desync issues:
- No escaping needed for any content (HTML, SX with newlines, quotes)
- No size limits (1MB+ responses work cleanly)
- No multi-line response splitting
- No double-escaping bugs
The old (ok "...") and (ok-raw ...) formats are still parsed as
fallbacks for backward compatibility.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>