Event names prefixed with $ are emitted by the SDK — avoid reusing them for custom events.

• $page — A page view.
• $identify — Emitted by identify().
• $group — Emitted by group().
• $exception — An error occurrence (powers Error tracking).
• $rageclick — A rage click (powers Frustrating pages).
• $api_request — An API request — method, path, status, durationMs (powers API performance).