pub fn set_current_account(npub: String) -> Result<(), String>Expand description
Set the currently-active npub for THIS process AND persist it to the
<app_data>/active_account marker so the next boot picks the same account.
Every call site asserts user intent (“this account is now active”); the
marker write is idempotent and gracefully no-ops when APP_DATA_DIR is
not yet configured (e.g. during in-process unit tests).