Zero-density exclusion drops a data-only copybook's COPY edge (CardDemo CSLKPCDY) #3417

Found by the mainframe ground-truth ledger on CardDemo. Cause: engine_excluded_copybook_edge.

Problem

app/cbl/COACTUPC.cbl line 602 contains COPY CSLKPCDY., and app/cpy/CSLKPCDY.cpy (1283 lines) exists, but the engine draws no edge to it. The statistical auditor puts it in excluded_artifacts as Zero-Density Threshold (LOC: 1283, Signals: 0). It is a phone area-code lookup table: pure VALUE data with no signals. Once the member is excluded, it is not a resolution target, and the edge from the program that copies it disappears.

This is 1 missed copybook edge on CardDemo. Any large data-only copybook (a lookup table or a code table) has the same exposure.

Question to settle

A copybook named by a COPY is a compile-time dependency whatever its signal density. The exclusion should probably drop the file from the density and risk statistics, not from the dependency graph. The alternative is to exempt resolved copy targets from the zero-density rule.

Acceptance

• The engine | copybook paths | app/cbl/COACTUPC.cbl | app/cpy/CSLKPCDY.cpy | fn ledger entry stops reproducing.
• A test: a data-only copybook with no signals, copied by a program, keeps its edge.

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