Keep an inline panel drawing when its host reports it hidden

Claude reports a panel on screen as hidden, which stopped the app's
render loop and the browser's animation frames, so no map was drawn. An
inline panel no longer suspends rendering when hidden, and draws from a
timer while animation frames stop arriving.

src/app/embed.test.mjs

@@ -1,6 +1,11 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
-import { applyView, installViews, isEmbedded } from './embed.js';
+import {
+  applyView,
+  installViews,
+  isEmbedded,
+  keepPanelRendering,
+} from './embed.js';
 import { createView } from '../view/index.js';
 
 const fakeViewer = () => {
@@ -159,6 +164,12 @@ test('an app loaded inline into a panel page talks through its own window', asyn
   windowRef.postMessage = (message) => posted.push(message);
   windowRef.document = { body: { classList: new Set() } };
   windowRef.document.body.classList.add = Set.prototype.add;
+  Object.assign(windowRef, {
+    requestAnimationFrame: () => 1,
+    cancelAnimationFrame() {},
+    setInterval: () => 1,
+    clearInterval() {},
+  });
   globalThis.GEV_EMBED_INLINE = true;
   try {
     assert.equal(isEmbedded({ search: '' }), true);
@@ -205,3 +216,33 @@ test('annotations in a link are drawn after it restores, embedded or not', async
     ['annotate_map', { annotations: [{ type: 'pin', target: 'Austin' }] }],
   ]);
 });
+
+test('a panel keeps drawing from a timer while animation frames stop', () => {
+  let clock = 0;
+  let tick = null;
+  let frame = null;
+  const windowRef = {
+    requestAnimationFrame: (fn) => ((frame = fn), 1),
+    cancelAnimationFrame: () => (frame = null),
+    setInterval: (fn) => ((tick = fn), 1),
+    clearInterval: () => (tick = null),
+  };
+  const drawn = [];
+  const viewer = {
+    resize: () => drawn.push('resize'),
+    render: () => drawn.push('render'),
+  };
+  const stop = keepPanelRendering(viewer, { windowRef, now: () => clock });
+  // Frames arrive: the render loop draws, so the timer does nothing.
+  clock = 100;
+  frame();
+  tick();
+  assert.deepEqual(drawn, []);
+  // Frames stop, as in a panel its host reports hidden: the timer draws.
+  clock = 400;
+  tick();
+  assert.deepEqual(drawn, ['resize', 'render']);
+  stop();
+  assert.equal(tick, null);
+  assert.equal(frame, null);
+});