Support dynamic session character set changes without reconnect.

Is there a way in WindTerm to dynamically reset the display character set of a session window? At the moment, I can only change the character set in the session properties and then reconnect to apply it. I frequently work with files in different encodings, and having to reconnect each time is a bit inconvenient.

No files, tests, or entry points are named. Start by tracing how session properties apply the display character set and how the session window handles reconnects; done means changing the character set takes effect without reconnecting and works when switching between differently encoded files.

Written by the indexing model from the issue text.