Port of retail gmMainChatUI::InitTalkFocusMenu @0x4cdc50 + HandleSelection
@0x4cd540 → SetTalkFocus. Button shows active channel label; click opens a
12-item popup that extends UPWARD (chat sits at screen bottom); selecting an
entry calls OnChannelChanged and updates Selected. BitmapFont? Font uses the
fully-qualified type name to match UiChatInput convention. Includes 6 xunit
tests covering channel table shape, default selection, and popup-pick routing.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
