Apply persisted Age lighting traits

docs/PORTING.md

@@ -269,6 +269,13 @@ symbol fallbacks: period 0.2–2.0, angle 0–360 degrees, and phase 0–1. Exis
 Ages load with normal Legacy defaults instead of being rerolled. This immutable
 trait layer is the foundation for applying each choice to modern worldgen.
 
+Version 0.2.18.0 applies each Age's persisted lighting trait to its runtime
+dimension. Normal Lighting retains Overworld skylight and ambient brightness;
+Bright Lighting uses Legacy's 0.25 ambient-light floor; Dark Lighting disables
+dimension skylight while retaining local block light. The latter is the closest
+server-safe modern equivalent to Legacy's removed per-dimension light-table
+scaling hook.
+
 Version 0.2.14.0 restores the legacy Linking and Descriptive Book artwork for
 inventory items and gives each book its matching open-book texture when placed
 on a Book Stand. Return Linking Books created inside another Age also retain and