River world hooks

- Skip nib, pothole, wall and slab post passes on river footprints and their collar
- Keep automatic object scatter off the channel and shore band
- Expose deeper biome layers on eroded banks and use the bank biome on the blend band
- Give dry cave headroom the flooded cave biome

core/src/test/java/art/arcane/iris/engine/IrisComplexSurfaceBiomeTest.java

@@ -21,7 +21,7 @@ import static org.mockito.Mockito.mock;
 
 public class IrisComplexSurfaceBiomeTest {
     @Test
-    public void gradingFootprintKeepsItsExactNaturalParentBiome() {
+    public void gradingFootprintUsesTheBankBiome() {
         HydrologyFeatureRef feature = new HydrologyFeatureRef(
                 1L,
                 HydrologyFeatureType.SURFACE_POOL,
@@ -65,7 +65,7 @@ public class IrisComplexSurfaceBiomeTest {
                 List.of(grading)
         );
 
-        assertEquals("exact_parent", IrisComplex.hydrologySurfaceBiomeKey(sample));
+        assertEquals("dry", IrisComplex.hydrologySurfaceBiomeKey(sample));
     }
 
     @Test

core/src/test/java/art/arcane/iris/engine/modifier/IrisPostModifierHydrologyTest.java

@@ -0,0 +1,20 @@
+package art.arcane.iris.engine.modifier;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class IrisPostModifierHydrologyTest {
+    @Test
+    public void columnsTouchingARiverFootprintSkipThePostPasses() {
+        assertTrue(IrisPostModifier.skipsHydrologyColumn(new double[] {1D, 0D, 0D, 0D, 0D}));
+        assertTrue(IrisPostModifier.skipsHydrologyColumn(new double[] {0D, 0D, 0.5D, 0D, 0D}));
+        assertTrue(IrisPostModifier.skipsHydrologyColumn(new double[] {0D, 0D, 0D, 0D, 0.75D}));
+    }
+
+    @Test
+    public void columnsAwayFromRiversKeepThePostPasses() {
+        assertFalse(IrisPostModifier.skipsHydrologyColumn(new double[] {0D, 0D, 0D, 0D, 0D}));
+    }
+}