fix(const-to-enum): handle boolean schema in properties (#1845)

JSON Schema allows `true` as a shorthand for an empty schema that
accepts any value. The `constToEnum` transformer was failing when
encountering such boolean schemas in properties because the `hasConst`
type guard assumed the input was always an object.

This adds a type check to handle boolean schemas gracefully, preventing
runtime errors during transformation.

---

### Ask Yourself

- [x] Have you reviewed the [contribution
guide](https://github.com/cdklabs/json2jsii/blob/main/CONTRIBUTING.md)?
- [x] Have you reviewed the [breaking changes
guide](https://github.com/cdklabs/json2jsii/blob/main/CONTRIBUTING.md#breaking-changes)?

Author: mrgrain

src/transformers/const-to-enum.ts

@@ -74,7 +74,7 @@ function transformConstToEnum(def: JSONSchema4): JSONSchema4 {
  * Type guard to check if the schema has a `const` property defined.
  */
 function hasConst(def: JSONSchema4): boolean {
-  return 'const' in def && def.const !== undefined;
+  return typeof def === 'object' && 'const' in def && def.const !== undefined;
 }
 
 /**

test/const-to-enum.test.ts

@@ -309,5 +309,19 @@ describe('constToEnum', () => {
       expect(result.oneOf?.[0].const).toBeUndefined();
       expect(result.oneOf?.[1].enum).toEqual(['b', 'c']);
     });
+
+    test('should handle required property with boolean true schema', () => {
+      const schema: JSONSchema4 = {
+        required: ['field'],
+        properties: {
+          field: true as any,
+        },
+      };
+
+      const result = constToEnum(schema);
+
+      expect(result.required).toEqual(['field']);
+      expect(result.properties?.field).toBe(true);
+    });
   });
 });

test/prohibited-names.test.ts

@@ -1,3 +1,4 @@
+import * as fc from 'fast-check';
 import { JSONSchema4 } from 'json-schema';
 import { TypeGenerator } from '../src';
 
@@ -106,8 +107,6 @@ describe('prohibited member names', () => {
 });
 
 
-import * as fc from 'fast-check';
-
 /**
  * Property-based tests for prohibited name handling
  * Feature: reserved-word-property-names