Derive the read limit from the accepted safe decimal PID plus a tolerated CRLF and overflow sentinel. Retain short-read handling, cached valid facts and existing descriptor ownership and handshake semantics. Fixes #5057
Derive the read limit from the accepted safe decimal PID plus a tolerated CRLF and overflow sentinel. Retain short-read handling, cached valid facts and existing descriptor ownership and handshake semantics. Fixes #5057