chat: ellipsize long model names in quick chat

Quick chat puts the input toolbars in the same row as the editor and
gives the editor whatever width the toolbars leave. A long model name
made the toolbars wider than the row, so the editor shrank to nothing
and the send button and the side actions were pushed out of view.

Cap the model name width in quick chat so it ellipsizes, like it does
in the chat view.

src/vs/workbench/contrib/chat/browser/widget/media/chat.css

@@ -2681,6 +2681,11 @@ have to be updated for changes to the rules above, or to support more deeply nes
 	align-items: flex-end;
 }
 
+/* The toolbars share a row with the editor here, so a long model name would push the actions out of view */
+.quick-input-widget .interactive-session .chat-input-picker-item .action-label.model-picker-split .model-picker-name {
+	max-width: 160px;
+}
+
 .quick-input-widget .interactive-session .chat-input-container {
 	margin: 0;
 	padding: 0 4px 0 6px;