Plugin SDK manifest schema additionalProperties:false not enforced

[intel352]

Context

Surfaced during P-DO PR #61: the workflow-plugin-digitalocean plugin.json's iacProvider block accepts extra keys (name, resourceTypes, configSchema) without validation error, despite the schema declaring additionalProperties: false.

Requested

Investigate whether the jsonschema library is honoring the constraint correctly, or if there's a schema-loading bug. Compare against draft-2020-12 spec interpretation.

Reference

• P-DO PR Global rate limiter state in module/api_gateway.go breaks plugin isolation #61
• workflow-plugin-digitalocean plugin.json