Free shipping fails at the equality boundary

Expected: shipping is free for a subtotal of at least 5000 integer cents. Observed in the starter: the calculation charges 500 cents at exactly 5000.

Reproduce with node --test issue.test.mjs. Preserve validation and all other fee rules. No database, network, real customer data, or account changes are involved.

Source, reproducibility and contributions

Commands, source code, sample prompts, identifiers and exact data remain in their original form so the exercises stay reproducible.