Describe the river placement, routing and grotto pool enums for the schema

core/src/main/java/art/arcane/iris/engine/object/IrisGrottoPoolLevel.java

@@ -1,5 +1,9 @@
 package art.arcane.iris.engine.object;
 
+import art.arcane.iris.engine.object.annotations.Desc;
+
+@Desc("Where the pool at the bottom of a coastal grotto sits.")
 public enum IrisGrottoPoolLevel {
+    @Desc("The pool surface sits at the dimension fluid height, so the grotto meets the sea.")
     SEA_LEVEL
 }

core/src/main/java/art/arcane/iris/engine/object/IrisRiverPlacementMode.java

@@ -1,9 +1,17 @@
 package art.arcane.iris.engine.object;
 
+import art.arcane.iris.engine.object.annotations.Desc;
+
+@Desc("Controls whether river sources may start inside a dimension, region or biome, and how strongly they are drawn there.")
 public enum IrisRiverPlacementMode {
+    @Desc("No river source may start here. Rivers may still pass through when routing allows it.")
     DISABLED,
+    @Desc("Rivers may pass through, but no source starts here.")
     TRANSIT_ONLY,
+    @Desc("Sources start here on their own merits, ranked like everywhere else.")
     NATURAL,
+    @Desc("Eligible source sites here rank ahead of sites elsewhere in the tile.")
     PREFERRED_HEADWATER,
+    @Desc("At least one source starts here whenever a site can reach a legal outlet; sources.minimumPerTile can raise that quota.")
     REQUIRED_HEADWATER
 }

core/src/main/java/art/arcane/iris/engine/object/IrisRiverRoutingMode.java

@@ -1,8 +1,15 @@
 package art.arcane.iris.engine.object;
 
+import art.arcane.iris.engine.object.annotations.Desc;
+
+@Desc("Controls whether river routes may pass through a dimension, region or biome, and at what cost.")
 public enum IrisRiverRoutingMode {
+    @Desc("Rivers never route through here.")
     BLOCK,
+    @Desc("Rivers route through here only when no cheaper path exists; transit carries a strong cost.")
     AVOID,
+    @Desc("Rivers route through here at the normal cost.")
     ALLOW,
+    @Desc("Rivers route through here at a reduced cost, so routes are drawn toward this area.")
     PREFER
 }