Java API: return EnumSort instead of DatatypeSort from Sort.create() (#10104)

`Expr.getSort()` on a constant with an `EnumSort` sort returns a
`DatatypeSort`, causing `ClassCastException` when enum-specific methods
are called.

```java
Context ctx = new Context();
EnumSort<Foo> enumSort = ctx.mkEnumSort("my-enum", "e1", "e2");
Expr<EnumSort<Foo>> c = ctx.mkConst("my-const", enumSort);
c.getSort().getName();  // ClassCastException — getSort() returns DatatypeSort, not EnumSort
```

### Changes

- **`Sort.java`**: In `Sort.create()`, detect enum sorts at the
`Z3_DATATYPE_SORT` case by checking whether all constructors have arity
0 — matching Z3's own `util::is_enum_sort` logic in
`datatype_decl_plugin.cpp`. Return `EnumSort<>` when true,
`DatatypeSort<>` otherwise.
- **`EnumSort.java`**: Add package-private `EnumSort(Context ctx, long
obj)` constructor so an `EnumSort` can be instantiated from an existing
native sort handle (analogous to `DatatypeSort(Context ctx, long obj)`).

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

src/api/java/EnumSort.java

@@ -92,6 +92,11 @@ public class EnumSort<R> extends Sort
         return new FuncDecl<>(getContext(), Native.getDatatypeSortRecognizer(getContext().nCtx(), getNativeObject(), inx));
     }
 
+    EnumSort(Context ctx, long obj)
+    {
+        super(ctx, obj);
+    }
+
     EnumSort(Context ctx, Symbol name, Symbol[] enumNames)
     {
         super(ctx, Native.mkEnumerationSort(ctx.nCtx(),

src/api/java/Sort.java

@@ -125,6 +125,17 @@ public class Sort extends AST
         case Z3_BV_SORT:
             return new BitVecSort(ctx, obj);
         case Z3_DATATYPE_SORT:
+            int n = Native.getDatatypeSortNumConstructors(ctx.nCtx(), obj);
+            boolean isEnum = true;
+            for (int i = 0; i < n && isEnum; i++) {
+                long ctor = Native.getDatatypeSortConstructor(ctx.nCtx(), obj, i);
+                if (Native.getDomainSize(ctx.nCtx(), ctor) != 0) {
+                    isEnum = false;
+                }
+            }
+            if (isEnum) {
+                return new EnumSort<>(ctx, obj);
+            }
             return new DatatypeSort<>(ctx, obj);
         case Z3_INT_SORT:
             return new IntSort(ctx, obj);