Static PASSKEY_SIGNAL_API_MODE 

pub static PASSKEY_SIGNAL_API_MODE: LazyLock<String>

Signal API mode for credential synchronization with authenticators.

Controls which WebAuthn Signal APIs are called for credential deletion and login sync:

• "direct": Use signalUnknownCredential only (default, currently the only working API with Google Password Manager)
• "sync": Use signalAllAcceptedCredentials only (currently no effect on Chrome, may work with other authenticators)
• "direct+sync": Use both APIs for maximum compatibility

Default: “direct”