Progress bar rendering issues

[Kostis-S-Z]

1. Progress bar writes emoji/control sequences to stdout, breaking piped/CI logs -> Recommendation: write progress to stderr and suppress it when the stream is not a TTY (the pip/git convention).

2. The emoji progress output cannot encode on default Windows consoles (cp1252) -> Recommendation: make the SDK's own printing encoding-safe (errors="replace" or an ASCII fallback) rather than requiring callers to set PYTHONUTF8.