enforce prototype builtin lint rule

eslint.config.mjs

@@ -321,7 +321,7 @@ export default [
 				"warn",
 				{ args: "none", varsIgnorePattern: "^_" },
 			],
-			"no-prototype-builtins": "off",
+			"no-prototype-builtins": "error",
 			"@typescript-eslint/no-empty-function": "off",
 			"@typescript-eslint/ban-ts-comment": [
 				"warn",

src/modals/taskModalFocusGuards.ts

@@ -272,6 +272,6 @@ function isInstanceOf<T extends Element>(
 ): element is T {
 	return (
 		element.instanceOf?.(constructor) === true ||
-		constructor.prototype.isPrototypeOf(element)
+		Object.prototype.isPrototypeOf.call(constructor.prototype, element)
 	);
 }