The navigation behavior after marking a message as unread is currently controlled via the static accessor: K9.messageViewPostMarkAsUnreadNavigation . This approach relies on legacy global state and bypasses the modern preference management architecture. As a result:

• It introduces tight coupling to the K9 class
• It is not lifecycle-aware
• It makes testing more difficult due to the lack of dependency injection
• It does not align with the current DataStore-based preference system

🎯 Goal

Replace the static accessor K9.messageViewPostMarkAsUnreadNavigation with a DataStore-backed preference, and update all usages across the application to access this value through the modern preference infrastructure