Creates the SecretsPlugin.
Registers an ISecretManager under CAPABILITIES.SECRETS. The
default provider is 'env' (zero dependency, every runtime), reading the
environment first and falling back to string config values when CONFIG is
registered. Set options.configFallback: false for environment-only reads.
Optionaloptions: SecretsPluginOptions
Plugin configuration
The plugin instance
SecretsPlugin factory — registers an
ISecretManagerunderCAPABILITIES.SECRETS.