OptionalfallbackOptionalworkspaceMemento used as the workspace-state fallback. Required when fallbackMode === 'workspace-state'.
OptionalmachineStable identifier mixed into the obfuscation key. Defaults to empty string. Pass vscode.env.machineId at the call site so a copied Memento does not open on a different machine. The machine id is not secret, so this does not protect against local access.
OptionalloggerLogger for fallback warnings.
OptionalonCalled once per instance when the fallback is first engaged. Inject the toast at the call site.
Fallback strategy when vscode.SecretStorage throws or is unavailable.