Merge main; keep inline panels polling while their host reports them hidden

Main now has #1282, which pauses periodic layer polling in a hidden page
with its own catch-up and listener cleanup, so this PR drops its duplicate
lifecycle.js change and test in favor of main's.

Review fixes:
- data.js passes panelAwareVisibility(document) (new in app/embed.js) as
  the lifecycle's visibility target, so an inline panel whose host reports
  it hidden keeps polling. The HUD's 250 ms readout follows the same
  document.hidden && !isEmbeddedInline() rule as tools.js.
- Tests: embed.test.mjs (layers poll in an inline panel reported hidden,
  pause without the flag) and hudPageVisibility.test.mjs (HUD readout).
  Both use mock timers and clean up in finally.
- changelog.d/1344-inline-panel-visibility.md and a note in
  docs/CURRENT-STATE.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/hudPageVisibility.test.mjs

@@ -0,0 +1,86 @@
+// The HUD's 250 ms telemetry readout skips ticks in a hidden page, except in
+// an inline panel, whose host may report it hidden while it is on screen.
+//
+// hud.js imports `mgrs`, which Node's ESM loader cannot read named exports
+// from, so a module hook swaps it for a stub before the import (the same
+// setup as hudAltitudeDatum.test.mjs).
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { registerHooks } from 'node:module';
+
+const MGRS_STUB_URL = 'gev-test-stub:mgrs';
+registerHooks({
+  resolve(specifier, context, next) {
+    if (specifier === 'mgrs') return { url: MGRS_STUB_URL, shortCircuit: true };
+    return next(specifier, context);
+  },
+  load(url, context, next) {
+    if (url === MGRS_STUB_URL) {
+      return {
+        format: 'module',
+        shortCircuit: true,
+        source: 'export function forward() { return "10SEG55776339"; }\nexport default { forward };\n',
+      };
+    }
+    return next(url, context);
+  },
+});
+
+const { IntelHUD } = await import('./hud.js');
+
+function installHiddenPage() {
+  const elements = new Map(
+    ['hud-alt', 'hud-summary', 'hud-mgrs', 'hud-latlon', 'hud-bottom-line', 'hud-gsd', 'hud-coll', 'hud-ona', 'hud-mode']
+      .map((id) => [id, { textContent: '' }]),
+  );
+  const previousDocument = globalThis.document;
+  globalThis.document = {
+    hidden: true,
+    visibilityState: 'hidden',
+    getElementById: (id) => elements.get(id) ?? null,
+    querySelectorAll: () => [],
+    addEventListener() {},
+    removeEventListener() {},
+  };
+  const viewer = {
+    camera: {
+      pitch: -Math.PI / 2,
+      positionCartographic: { latitude: 0.7, longitude: -1.2, height: 500 },
+      computeViewRectangle: () => undefined,
+      moveEnd: { addEventListener() {}, removeEventListener() {} },
+    },
+  };
+  return {
+    alt: () => elements.get('hud-alt').textContent,
+    viewer,
+    restore() {
+      if (previousDocument === undefined) delete globalThis.document;
+      else globalThis.document = previousDocument;
+    },
+  };
+}
+
+test('the HUD readout pauses in a hidden page but keeps updating in an inline panel', (t) => {
+  t.mock.timers.enable({ apis: ['setInterval'] });
+  const page = installHiddenPage();
+  let hud;
+  try {
+    hud = new IntelHUD(page.viewer);
+    hud._visible = true;
+
+    t.mock.timers.tick(250);
+    assert.equal(page.alt(), '', 'a hidden page skips the telemetry tick');
+
+    globalThis.GEV_EMBED_INLINE = true;
+    t.mock.timers.tick(250);
+    assert.match(
+      page.alt(),
+      /^ALT: 500m/,
+      'an inline panel reported hidden keeps its readout updating',
+    );
+  } finally {
+    delete globalThis.GEV_EMBED_INLINE;
+    hud?.destroy();
+    page.restore();
+  }
+});