Pin feature ordering to vanilla runtime

internal/world/feature_sorter_test.go

@@ -0,0 +1,28 @@
+package world
+
+import (
+	"slices"
+	"testing"
+
+	"regionio/internal/worldgen"
+)
+
+func TestOverworldFeatureStepsBuildWithoutCycles(t *testing.T) {
+	set, err := worldgen.LoadFeatureSet()
+	if err != nil {
+		t.Fatal(err)
+	}
+	steps, err := set.FeatureSteps(possibleBiomeOrder())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(steps) != 11 {
+		t.Fatalf("feature steps = %d, want 11", len(steps))
+	}
+	ores := steps[undergroundOresStage]
+	for _, name := range []string{"minecraft:ore_clay", "minecraft:ore_diamond", "minecraft:ore_tuff"} {
+		if !slices.Contains(ores, name) {
+			t.Errorf("underground ores missing %s", name)
+		}
+	}
+}