JSON.parse keeps the last of two equal keys and says nothing, so a duplicate silently kills the first entry
while every gate that reads the parsed object passes. "check:religion-label-not-value" sat twice in
//scripts after a merge (found by regions-plugin; only Bun's parser warned). A small scanner tracks keys
per object; its self-test runs on every invocation, and a planted duplicate is caught. In gates:pre.
The landing tooling's package.json union now refuses to write a result with a repeated key.
