Function login_with 

pub async fn login_with<H, C, B, X>(
    http: &H,
    clock: &C,
    hooks: LoginHooks<'_, B>,
    cancel: &X,
    persist: bool,
) -> Result<OAuthCredentials, CopilotAuthError>
where
    H: CopilotHttp,
    C: CopilotClock,
    B: CopilotBrowser,
    X: CopilotCancel + ?Sized,

Device start → user prompt → poll → mint → atomic persist.