fix: le resultat d-une commande de page suit la meme regle que tout le reste

Balayage execute sur les deux proxys apres le correctif precedent : aucun membre
de la vue de collection ne rend plus la cible, mais une commande de page de
l-enveloppe qui rendrait la collection la rendait BRUTE. `nextPage` est declare
`() => void` et ne rend rien aujourd-hui, donc ce n-est pas un defaut vivant -
c-est la meme justification jamais executee, sur l-autre proxy, et c-est
exactement le motif qu-il fallait casser. Elle s-execute toujours ; seul son
retour est tenu a la regle.

packages/polyfill/src/emulated-verifier/read-filter.ts

@@ -500,12 +500,24 @@ export function makeReadFilteredShapeResult<R extends object>(result: R, caps: C
           "`useShapeQuery`.",
       );
     }
-    // THE PAGE COMMANDS. They return `void` and yield nothing, so they forward, exactly
-    // as `add`/`delete`/`clear` do on the collection view. What they load lands in the
-    // raw collection, which is only ever read back through the filter above.
+    // THE PAGE COMMANDS. They forward: what they load lands in the raw collection, which
+    // is only ever read back through the filter above.
+    //
+    // Their RESULT is held to the same rule as everything else here, and that is the
+    // lesson of the collection view rather than a worry about this one. `nextPage` is
+    // declared `() => void` and the shipped hook assigns the subscription's own, so today
+    // it yields nothing - but "it returns void" was the written, unexecuted ground on
+    // which `add` was forwarded, and `Set.prototype.add` returns the collection. A page
+    // command that ever hands something back gets the same answer as any other member:
+    // a scalar passes, anything that could reach an item refuses.
     if (prop === "nextPage" || prop === "previousPage") {
       const fn = Reflect.get(target, prop, target);
-      return typeof fn === "function" ? fn.bind(target) : fn;
+      if (typeof fn !== "function") return fn;
+      return (...args: unknown[]): unknown => {
+        const out = (fn as (...a: unknown[]) => unknown).apply(target, args);
+        if (cannotReachAnItem(out)) return out;
+        throw refusalOf(prop, "the result envelope");
+      };
     }
     return answerUnnamedMember(target, prop, "the result envelope");
   };