Covers the POP3 TRANSACTION state machine via scripted sessions over
net.Pipe, mirroring the SMTP handler test harness: STAT/LIST/UIDL/DELE/
RETR/TOP/NOOP/RSET/QUIT including argument error paths, deleted-message
behavior, dot-stuffing, RETR/TOP source error paths, mailbox load
errors, session read error handling (idle timeout vs other), and the
TCP listener lifecycle (Start/serve/Notify/Drain).
No production code changes; current behavior is pinned as-is. Two
known RFC deviations are documented in tests (RETR/TOP of messages
marked deleted) for follow-up fixes. Package coverage: 24.4% -> 93.2%.
Signed-off-by: James Hillyerd <james@hillyerd.com>
James Hillyerd