[iamnbutler]

Shows who is typing in a chat, just above the composer (ChatStatus with TypingDots, previously unused). Closes part of #35.

• The channel gets a typing request and a live typing event. A watch opts in with typing: true, so older clients never see the event. Nothing is stored: the worker sends the event to that chat's other watchers and drops it.
• It rides the existing channel request and watch path, so the gateway stamps the author, and teammates watching through a peer get it through the same relay. It needs no directory or lobby. packages/channel stays runtime-neutral.
• The app sends a signal at most every 3 s while the composer has unsent text and the chat is ready. Viewers drop a typist 5 s after their last signal, or as soon as that person's message lands, and never show themselves.
• Demo mode gets a type step, documented in docs/demo.md.

Smoke-tested from this lane on a loopback ace serve --demo host:

• A demo teammate's typing showed ace-demo-rivera is typing. It cleared the instant their message landed, and went stale 5.2 s after a lone signal.
• Typing in the app produced typing events from iamnbutler@gmail.com at 0, 3 and 7 s on a raw gateway watch.

Not smoked: a teammate on another host through a peer relay. It uses the same channel request path as say.

Built in Ace

No: Claude Code (the ace2-90 fix-train session) wrote and smoke-tested this through a headless demo host, Playwright and a gateway watch. See #5.