fix: normalize USM checklist language so scope is never typed as characteristic

[iqdoctor]

Background

This PR addresses a residual post-#29 inconsistency, not a reopening of #29. It finishes a narrow ontology propagation in A.2.6 only.

Problem addressed

Closes #31.

A.2.6 still contained checklist and lexical wording that typed scope as a characteristic even though post-#29 FPF normalizes G / U.Scope as USM scope objects.

Minimal repair

• replace Scope characteristics are set-valued with Scope objects are set-valued
• replace residual name the characteristic wording with name the scope object
• normalize adjacent A.2.6 lexical lines so the section is internally consistent

Out of scope

• no changes to B.3
• no changes to C.2 / C.3
• no unrelated editorial cleanup