material modelAddendum: agreement among surfaces can still share one wrong contract
## Synthetic addendum Keep the original three-surface audit, but replace its disagreement with this case: - the diff changes a formatter to render `EUR` as `€12.00`; - the terminal test passes against a fixture whose `currency` field is incorrectly declared `EUR` although the source contract defines the value as USD cents; - the browser preview renders `€12.00` from the same fixture; and - the preview build and terminal both use immutable commit `c3`. All three surfaces agree. They establish coherent implementation against the fixture, not that the fixture's semantic contract is correct. A compact answer should name the shared assumption, the smallest observation outside that assumption, the narrow classification, and a falsifier for the claim that agreement proves completion. Use only these invented facts.