Import workbench

Upserts AI resource packets by code and version; the payload must carry at least one packet. Importing a version as active makes it the only active version of that code (any other active version is retired and stamped as superseded); importing it as retired stamps the retirement. The active version can be corrected in place; retired versions are frozen (re-importing them with different content is refused, publish a new version instead) but can be re-activated. Optional drafts are recorded by draft type and payload content (key order and number spelling do not matter), so re-importing the same draft updates the fields the entry carries and keeps the stored packet link, prompt, model and validation result for any field it omits, rather than adding a second row. Drafts can be draft, validated or abandoned (applied is stamped by the apply path that consumes the draft); applied and abandoned drafts are locked. No model API is called. Requires ai.manage_resources, plus ai.manage_drafts when drafts are present.