RFE: Independent Chat [Floating] Window

I'd like to see an independent floating window (resizable and movable) that is always visible at each phase of the game. When changing turns, it is difficult to type a message while changing phases when I need to reopen the chat window.

No files, tests, or entry points are named. Start by tracing the Java client’s existing chat window and the turn/phase transitions; done means chat remains visible in a movable, resizable independent window throughout every game phase.

Written by the indexing model from the issue text.