- Ctrl+D in the Single URL field runs a handshake probe against the typed endpoint. It detects HTTP and/or SOCKS5 without forwarding traffic or contacting external hosts.
- HTTP-capable endpoints map to http://; SOCKS5-only endpoints map to socks5h://. Userinfo is preserved as typed.
- Bare host:port input is accepted and defaults to http:// at save.
- Update README privacy boundary and add .scratch/protocol-probe/spec.md.