Broaden copy-paste pattern to near-duplicate line verification

The old "copy-paste errors" pattern only covered wrong variables in null
checks. GPT-5.4 missed bugs where: a null check used the wrong variable
from an adjacent line, a bulk delete used the wrong type filter, and
metric tags were inconsistent across similar statements.

Generalized to: when similar statements appear together, verify each
line's differentiating detail independently (variable, predicate, string
literal, scope). This covers null checks, filter conditions, metric tags,
and any repetitive code where the per-line detail diverges.