High CPU usage in irc.server.

The `select()` call returns immediately almost always, since the sockets are usually `ready_to_read`. This effectively creates a tight loop and very high CPU usage for any active connection.

Start by locating the irc.server select() loop and inspect why sockets remain ready_to_read across iterations. Reproduce the behavior with an active connection and verify that the loop no longer spins continuously or causes high CPU usage; add a regression test if the existing test structure covers this path.

Written by the indexing model from the issue text.