fix: address Copilot review round 26 — a false property schema declines the branch

JSON Schema's boolean form is legal, but only `true` is harmless: it
constrains nothing, while `false` admits no value at all — so a field
declared with it can never be filled, and a required one makes the whole
branch unsatisfiable. Offering it contradicted every other faithfulness check
in the resolver, so such a branch is declined.

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

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

@@ -764,9 +764,9 @@ describe("resolveRootUnion", () => {
       }
     });
 
-    it("offers a member carrying a boolean property schema", () => {
-      // JSON Schema's boolean form is legal and answers every keyword lookup
-      // with `undefined`, so it renders through the JSON fallback harmlessly.
+    it("offers a member carrying a `true` property schema", () => {
+      // `true` constrains nothing and answers every keyword lookup with
+      // `undefined`, so it renders through the JSON fallback harmlessly.
       const { branches } = resolveRootUnion({
         type: "object",
         anyOf: [
@@ -777,6 +777,19 @@ describe("resolveRootUnion", () => {
       expect(branches).toHaveLength(2);
     });
 
+    it("declines a member carrying a `false` property schema", () => {
+      // `false` admits no value at all, so the field can never be filled — and
+      // a required one makes the branch unsatisfiable.
+      const { branches } = resolveRootUnion({
+        type: "object",
+        anyOf: [
+          { type: "object", properties: { nothing: false } },
+          { type: "object", properties: { other: { type: "string" } } },
+        ] as unknown[],
+      });
+      expect(branches).toEqual([]);
+    });
+
     it("declines a member whose properties are not an object", () => {
       // Members arrive as `unknown`, so this is reachable and must not throw.
       expect(

core/json/rootUnion.ts

@@ -180,15 +180,17 @@ function isOfferable(branch: RootUnionSchema): boolean {
   const properties = Object.values(propertiesOf(branch));
   return (
     properties.length > 0 &&
-    // Every value has to be something a renderer can read. JSON Schema's
-    // boolean form is legal and harmless — `true`/`false` answer every keyword
-    // lookup with `undefined` — but a `null` or an array is not a schema at
-    // all, and the web form dereferences one on the way to choosing a widget.
-    // A branch carrying one is declined rather than handed on to crash a tool
-    // panel that would otherwise have rendered.
+    // Every value has to be something a renderer can read AND something a
+    // caller can satisfy. A `null` or an array is not a schema at all, and the
+    // web form dereferences one on the way to choosing a widget. JSON Schema's
+    // boolean form is legal, but only `true` is harmless — it constrains
+    // nothing and answers every keyword lookup with `undefined`, while `false`
+    // admits no value whatsoever, so a field declared with it can never be
+    // filled and a required one makes the whole branch unsatisfiable. Either
+    // way the branch is declined rather than offered as a callable shape.
     properties.every(
       (property) =>
-        typeof property === "boolean" ||
+        property === true ||
         (typeof property === "object" &&
           property !== null &&
           !Array.isArray(property)),