Chat mockup

Wrap the thread in a bare, sequenced koala-mockup. Each koala-mockup-chat-bubble appears at its at step; typing-at holds its place with typing dots first, and an outgoing bubble's ticks turn read at read-at.

name and status fill the header, channel sets the icon on its right, and day adds a date chip above the first message. Without an avatar URL the header shows the contact's initial. A bubble at step 0 shows from the start, so a thread that should simply sit still needs only one long step.