A PART event from the user's own nick now closes the channel's tab,
whether this web client or another client of the session sent it. It
adds no message or unread count.
A KICK event now goes into the channel's tab as "nick was kicked from
channel by kicker (reason)", with the kicked nick taken from params.
Before, it fell through to the Server tab, which showed only the
reason. When the kicked nick is the user's own, the tab closes.
The tab removal that partChannel did moves into removeChannelTab,
which partChannel and both events share.
Model: opus-5-5
sneak