fix: preserve PTY output for Windows SSH sessions

[sitiom]

sshpass-win32 suppresses child PTY output while scanning for authentication prompts. That prevented terminal control sequences from reaching the local console during session setup, leaving Windows OpenSSH in the wrong input mode and sending interactive keys such as Up/Down/Left/Right as literal sequences like [A and [C.

• Always pass child PTY output through to stdout instead of hiding it during prompt detection.
• Keep password prompt hiding with a minimal output filter, rather than suppressing PTY output wholesale.
• Revert to forwarding stdin to the child PTY as raw bytes using ReadFile.