Add AP242 styled_item functional test infrastructure
Test both vanilla AP242 schema (needs flow-sensitive narrowing)
and modded schema that is more strictly compliant.
Both schema tests use same STEP file
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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: starseeker <238416+starseeker@users.noreply.github.com>
