fix: remove redundant undefined check in urgencyLabel (#90)

The parameter type is number | null, so undefined is impossible.
Simplify to == null (covers both) to resolve CodeQL code quality
finding js/unneeded-defensive-code.

Author: TommiLindfors

packages/generator/src/generator.ts

@@ -296,7 +296,7 @@ function mergeExplanationTraces(
 // ── Urgency label from score ─────────────────────────────────────────
 
 function urgencyLabel(score: number | null): string | null {
-  if (score === null || score === undefined) return null;
+  if (score == null) return null;
   if (score >= 90) return "urgent";
   if (score >= 70) return "important";
   if (score >= 40) return "standard";