CommandToggles

Pinned commands for the leftActions slot of the composer. One command is active at a time; clicking it again clears it, and onChange receives null. Pass value and onChange to control it, or defaultValue to let it keep its own choice. The kit only shows the choice: add the command to the message yourself in onSend. Each button reports aria-pressed, description becomes a tooltip on hover and keyboard focus that is also the accessible description, and disabled keeps a command visible but inert. On narrow composers the row scrolls sideways instead of wrapping.