Chat tab management

The Chat Window tab management is very poor.

A user should be able to perform common chat tab options with keyboard shortcuts (switch tabs, close current tab, close all tabs, reopen a closed tab), group tabs up, and reference tabs or tab groups as context for other chats with drag and drop.

The issue names no files, tests, or entry points. Start by locating the Chat Window tab-management implementation and its existing keyboard and drag-and-drop handling; clarify the intended behavior for switching, closing, reopening, grouping, and sharing tab context before defining tests for each completed interaction.

Written by the indexing model from the issue text.