Bead: av-r0s.1

Summary:

• Add optional rubric criterion operator metadata for correctness/contradiction semantics.
• Preserve operator meaning through parsing, schema validation, LLM grader prompt construction, docs, and skill schema references.
• Add regression coverage for parser/schema/prompt/YAML loading.

Verification from worker handoff:

• focused operator suite
• bun run verify
• bun run validate:examples
• CLI fixture dry run with mock target

Integration review: branch is 0 behind / 1 ahead of current origin/main.