Moves the Zap button and Zap statistics from the message thread header to the message composer area, adjacent to the Send button. Refactors the Zap interface creation logic into a standalone component `ZapInterface.js` to decouple it from `MessageThread.js`. Updates `Composer.js` to support an optional `onZap` handler and `zapStats` prop, rendering the button with an icon-only style and the stats pill reusing the existing CSS class. Updates `AppShell.js` to orchestrate the Zap interface display and pass the necessary statistics.