fix(utils): use Zone.js unpatched MutationObserver on Safari

[d0ugal]

Problem

When Angular's Zone.js is present, it monkey-patches MutationObserver. rrweb's getUntaintedPrototype detects the patched version and falls back to creating a hidden iframe, then uses iframe.contentWindow.MutationObserver to get an unpatched observer.

On Safari/WebKit, a MutationObserver obtained from an iframe's contentWindow silently never fires callbacks when observing nodes in the parent document. This means rrweb captures zero DOM mutations — full snapshots work, but all incremental changes are lost.

Fix

Zone.js stores original unpatched globals under globalThis[Zone.__symbol__(key)]. Before attempting the iframe fallback, check if Zone.js has stored the native MutationObserver and use it directly.

const zoneAlternative = angularZoneUnpatchedAlternative(key);
if (zoneAlternative) {
  return zoneAlternative.prototype;
}

This is the same approach used by PostHog: PostHog/posthog-js#1687

Testing

Verified with Angular apps (Zone.js present) across Chrome, Firefox, and Safari (Playwright WebKit). After the fix, Safari sessions capture 146+ mutations where previously they captured zero.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 5b25627

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR