test(main): completar fase 2 con cobertura de iconos y timing

src/main/utils/timing.ts

@@ -0,0 +1,3 @@
+export function getRemainingDelayMs(targetDelayMs: number, startedAtMs: number, currentTimeMs: number = Date.now()): number {
+  return Math.max(0, targetDelayMs - (currentTimeMs - startedAtMs));
+}