Channel surfing for Expo Updates: How to switch update channels at runtime

Expo's new 'channel surfing' feature lets installed apps switch EAS Update channels at runtime without reinstalling. Using the `setUpdateRequestHeadersOverride` API, developers can direct specific users (QA, product owners, stakeholders) to pull updates from a different channel like `preview` instead of `production`. The typical flow involves setting the channel override, checking for an update, fetching it, and reloading the app. The post covers implementation details, how to test with EAS Build simulator profiles, and important gotchas like runtime version mismatches and how update deletion works on already-downloaded updates.