validate-plugin

Validate a new or changed agentz plugin before publishing by writing its Vally evals, running them, running the marketplace gate locally, and producing a publish-readiness report. Use when the user says "validate my plugin", "write evals for this skill", "is my plugin ready to publish", or after build-plugin finishes. This is phase 4 of 4 (Analyse, Research, Build, Validate). Do not use to review someone else's pull request.