Schedule Always Snow with season integrations

docs/PORTING.md

@@ -24,7 +24,9 @@ split into independently testable milestones.
    dimension-type, and worldgen configuration. Optional integrations with
    TerraBlender provide composable biome-region generation, while Serene
    Seasons and Ecliptic Seasons allow Age generation to participate in their
-   respective seasonal systems. None of these integrations are required for
+   respective seasonal systems. True Always Snow weather will be introduced
+   with these season integrations; until then, its persisted trait uses
+   biome-dependent precipitation. None of these integrations are required for
    Rivencraft's core world generation.
 6. **Instability** — deterministic validation and effects with server-safe
    behavior.