test: cover the non-object property-declaration paths in rootUnion

The previous commit's coverage gate failed on `core/json/rootUnion.ts`
branches (89.81%). A property declared with JSON Schema's boolean form has no
keywords to merge, so the two sides agree only by being the same declaration —
now tested both ways, and the dead `baseProperty !== undefined` guard is gone
(`conflicts` is only reached for a name the base declares).

Signed-off-by: cliffhall <cliff@futurescale.com>

clients/web/src/test/core/rootUnion.test.ts

@@ -202,6 +202,33 @@ describe("resolveRootUnion", () => {
     });
   });
 
+  it("carries an identical non-object declaration across", () => {
+    // JSON Schema's boolean form is legal as a property schema. There are no
+    // keywords to merge, so the two agree only by being the same declaration.
+    const { branches } = resolveRootUnion({
+      type: "object",
+      properties: { x: true as unknown },
+      anyOf: [
+        { type: "object", properties: { x: true as unknown } },
+        { type: "object", properties: { other: { type: "string" } } },
+      ],
+    });
+    expect(branches).toHaveLength(2);
+    expect(branches[0].schema.properties?.x).toBe(true);
+  });
+
+  it("declines a union whose branch redeclares a non-object property differently", () => {
+    const { branches } = resolveRootUnion({
+      type: "object",
+      properties: { x: true as unknown },
+      anyOf: [
+        { type: "object", properties: { x: false as unknown } },
+        { type: "object", properties: { other: { type: "string" } } },
+      ],
+    });
+    expect(branches).toEqual([]);
+  });
+
   it("declines a union whose branch contradicts the root's type for a field", () => {
     // `string` under a base `number` describes a value that cannot exist, so
     // flattening it would render one type and accept what the schema rejects.

core/json/rootUnion.ts

@@ -183,9 +183,11 @@ function conflicts(baseProperty: unknown, branchProperty: unknown): boolean {
   const a = toBranch(baseProperty);
   const b = toBranch(branchProperty);
   if (a === null || b === null) {
-    return (
-      baseProperty !== undefined && !sameValue(baseProperty, branchProperty)
-    );
+    // At least one side is not a readable schema object — JSON Schema's boolean
+    // form, or something malformed. Nothing can be merged keyword-wise, so the
+    // two agree only if they are the same declaration. (Only reached for a name
+    // the base declares, so `baseProperty` is never simply absent here.)
+    return !sameValue(baseProperty, branchProperty);
   }
   const left = a as Record<string, unknown>;
   const right = b as Record<string, unknown>;