27 test fixtures (11 valid + 16 invalid) and a test runner that
exercises the forthcoming Zod schema for workflow.yaml files.
Includes a stub schema that fails all validation, confirming
26 failing / 1 passing (yaml-parse-error) — TDD red state.
Follows the validate-agent-schema pattern (tools/schema/agent.js,
test/test-agent-schema.js).
Ref: MSSCI-12749
Michael Pursifull