Provider.ensure_schema(context) remains callable from workspaces. Rename the provider hook to a private SPI, require an internal capability token, and keep UserContext.ensure_schema() as the only public application entry point. Add negative surface tests.
Provider.ensure_schema(context) remains callable from workspaces. Rename the provider hook to a private SPI, require an internal capability token, and keep UserContext.ensure_schema() as the only public application entry point. Add negative surface tests.