test(browser): compare ax.find across both hosts on one page

test/browser/testdata/find-order/index.html

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+<!doctype html>
+<html>
+  <body>
+    <!-- Two elements share the id, one inside a shadow root on the mount and
+         one later in the light DOM. The hierarchy dump orders a host's shadow
+         children before its light ones, so a pre-order search there reaches the
+         shadow one first; a light-DOM sweep that only descends afterwards
+         reaches the other. The page exists to make the two walks disagree. -->
+    <div id="mount" style="width: 200px; height: 80px"></div>
+    <span id="x">light</span>
+    <script>
+      document.getElementById("mount").attachShadow({ mode: "open" }).innerHTML =
+        '<span id="x">shadow</span>';
+    </script>
+  </body>
+</html>

test/browser/testdata/find-order/spec.ts

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+import { always, extract, taps } from "@sanderling/spec";
+
+// Which of the two #x a selector means is the whole fixture. The reading is
+// compared between the two hosts by TestBrowserAxFindAgreesAcrossHosts, which
+// drives each host's production path and never asks one what the other said.
+//
+// Written in the "k:v" string grammar because that is the one form both hosts
+// resolve the same way: the object form {id: "x"} reaches the goja host as a
+// plain attribute filter, and a web hierarchy dump carries the id under
+// resource-id, so it matches nothing there.
+const found = extract((s) => s.ax.find("id:x")?.text).named("found");
+
+const findsTheShadowMatch = always(() => found.current === "shadow");
+
+export const properties = { findsTheShadowMatch };
+
+export const actionsRoot = taps;