fix(tests): stop hls_qa deep-probe suite hanging under jsdom

CI times out on the 7 "HLS QA: Deep probe strategies" tests. Root cause
is a jsdom-only artifact, not a production bug: jsdom exposes the
self-referential cyclic globals (_globalObject/_globalProxy/_top/_parent/
window/self/top/parent/frames) as ENUMERABLE own-props on the window.
Strategy H in m3u8DeepProbeFn() runs Object.keys(window) and a no-
visited-set walk() over each, which explodes to O(204^5) ≈ 3.5e11 ops and
never terminates within the depth-5 cap, so the whole suite hangs forever.

A real Chrome MAIN-world window does NOT expose those keys as enumerable
own-props, so this is purely a test-environment mismatch. The fix is
test-only: sanitizeJsdomWinForProbe() marks the jsdom cyclic globals
non-enumerable in runProbeInWin() before eval, mirroring a real page.
No production/underlying source (src/viewer/index.js) is modified.

Local (Node 22.22.3 / Linux == CI ubuntu-latest + Node 22):
before: npm test hangs indefinitely (no Results line; CI job killed)
after:  npm run build && npm test -> 83/83 passed in ~12.5s

__tests__/hls_qa.test.mjs

@@ -679,8 +679,43 @@ if (!probeMatch) {
 }
 const probeFnSource = probeMatch[0];
 
+// jsdom exposes a set of self-referential cyclic globals as *enumerable own-*
+// properties on the window object. A real Chrome MAIN-world window does not:
+// `window`, `self`, `top`, `parent`, `frames` are non-enumerable, and the
+// jsdom-internal `_globalObject`/`_globalProxy`/`_top`/`_parent` keys don't
+// exist at all. The deep-probe's Strategy H runs `Object.keys(window)` and a
+// no-visited-set `walk()` over each player-like value, so these cyclic
+// jsdom-only keys make the walk explode to O(keys^depth) (~3.5e11 ops) and the
+// suite never terminates. We can't fix the probe (production src/ is off-limits
+// for this test-only PR), so instead we make this jsdom window mirror a real
+// page by marking the cyclic globals non-enumerable before the probe runs.
+const JSDOM_CYCLIC_GLOBALS = [
+  '_globalObject', '_globalProxy', '_top', '_parent',
+  'window', 'self', 'top', 'parent', 'frames',
+];
+function sanitizeJsdomWinForProbe(win) {
+  for (const key of JSDOM_CYCLIC_GLOBALS) {
+    if (!Object.prototype.hasOwnProperty.call(win, key)) continue;
+    let desc;
+    try { desc = Object.getOwnPropertyDescriptor(win, key); } catch { continue; }
+    if (!desc) continue;
+    try {
+      // Re-assert the same descriptor but with enumerable:false so the probe's
+      // `Object.keys(window)` no longer sees jsdom's cyclic self-references.
+      Object.defineProperty(win, key, { ...desc, enumerable: false });
+     } catch {
+       // Non-configurable descriptors (e.g. the `window`/`top` getters) can't be
+       // redefined; skip them. The remaining cyclic keys are already suppressed,
+       // leaving only a shallow 2-branch recursion that terminates in ms.
+     }
+   }
+}
+
 // Helper: eval the probe function inside a JSDOM window, then return results
 function runProbeInWin(win) {
+  // Mirror a real page environment (see JSDOM_CYCLIC_GLOBALS note above):
+  // non-enumerable cyclic globals prevent Strategy H's window scan from looping.
+  sanitizeJsdomWinForProbe(win);
   // Define the function in the JSDOM context and call it
   const result = win.eval(`
     (${probeFnSource})();