Stream updates

renderStream() applies a <webjs-stream action="..." target="..."> payload: a surgical, element-level DOM update by id. Each button below mutates the live list in place, and the component never re-renders (contrast a frame, which swaps a whole region, and the client router, which swaps a whole page).

The same grammar arrives over HTTP (a content-negotiated <form> response the router applies surgically, degrading to a full round-trip with JS off) and over a live channel (a broadcast() message applied with renderStream() from a connectWS handler, see the WebSockets card).