Adds test coverage for the case where a YAML number value appears
in the variables record (e.g., `count: 5`). YAML parses unquoted
numbers as integers, which the schema correctly rejects as
invalid_type (expected string, received number). This is a likely
contributor mistake worth covering.
28/28 fixtures now passing.
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