Persist random Age traits

docs/PORTING.md

@@ -262,6 +262,13 @@ from Book Stands. Snapshot chunk loading is independent from whether the Explore
 control is enabled, so mounted books retain live terrain without allowing the
 player to enter Explore mode.
 
+Version 0.2.17.0 begins persistent random Age traits. New page-free Ages select
+and save a legacy-inspired biome distribution, lighting mode, weather mode, and
+celestial period, angle, and phase. The celestial ranges follow Legacy's random
+symbol fallbacks: period 0.2–2.0, angle 0–360 degrees, and phase 0–1. Existing
+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 0.2.14.0 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