Manifest schema, checksum, path-safety and reserved-namespace validation for drop-in plugin bundles (PLAT-12). A thin, zero-additional-dependency validator: it depends only on ravenroot-application-api, reusing PayloadJson/PayloadValue/PayloadLimits for manifest parsing rather than adding a YAML or JSON Schema library. Deliberately does not depend on ravenroot-core: this module never loads a class, never touches NodePackage/NodePackages, and is callable ...