fix: normalize G as scope object and add CoverageMetric(G) guardrail

[iqdoctor]

Summary

This PR now applies the full minimal repair set for the G ontology inconsistency.

Changes

1. In B.3, replaced the triad formula from characteristic-only framing to:
   • two characteristics (F, R) + one scope object (G).
2. In A.2.6:7.4 (FPF-Spec.md:4030), replaced:
   • set-valued characteristic -> set-valued scope object.
3. Introduced explicit projection CoverageMetric(G) as an optional report-only proxy and added a hard normative guardrail:
   • CoverageMetric(G) MUST NOT substitute G in norms, gate predicates, or conformance logic.

Why

The spec previously mixed two incompatible typings for G:

• CHR-style “characteristic” language in B.3,
• USM scope-object typing in A.2.6 / C.2.2 constraints.

This PR makes the typing explicit and consistent while preserving existing gate/bridge behavior (CL penalties still affect R only).

Scope

• Ontology/wording consistency and normative typing guardrails.
• No algorithmic runtime changes.

Related: #29