type separation

Some harness values look alike while carrying authority that must never substitute for one another.

This home owns directional challenges for those boundaries. Each row names the type a position requires, the type that must be refused there, and the semantic distinction the refusal protects. Direction matters: a challenge says nothing about offering the two types in the opposite order.

Evidence ceiling

A row is authored input to a compiler-refusal observation, not the observation itself. Holding the bank establishes neither that a generator consumed every challenge nor that rustc rejected one, and a separation proved elsewhere is not weakened by having no row here.