Port seeded random Ages and authored Rocks to 26.3 beta

docs/MINECRAFT_26_3_PORT.md

@@ -508,6 +508,20 @@ versions.
 The local `1.0.1.39-beta.1` follow-up makes the 26.3 landing search reject
 fluid at feet and head height and prevents a submerged fallback platform.
 
+The local `1.0.1.40-beta.1` slice gives pageless Descriptive Books a
+seed-selected terrain and biome plan. It follows the 1.21.1 rank weights for
+terrain and biome distribution, selects registered Cave/Nether biomes for Cave
+Ages and overworld-source biomes for other non-Void terrains, and persists the
+resolved choices. Other random Age traits remain a later port task.
+
+The local `1.0.1.41-beta.1` slice adds the first Age-scoped feature wrapper to
+the 26.3 generator. A Block page followed by Rocks now places clusters of the
+chosen block in new Standard, Amplified, Island, or Flat terrain chunks. The
+Age index persists that selection, and the wrapper delegates all vanilla
+terrain, biome, and structure generation. Cave and Void are intentionally
+excluded until their feature placement rules are ported. This is not yet the
+full 1.21.1 feature grammar or instability system.
+
 ## Verification of this first slice
 
 The 1.21.1 `compileJava` and `build` tasks passed offline after the backend