DropdownMenu inside Modal causes scroll-to-top on iOS Safari when using two-phase activation

[malinindev]

We use a two-phase activation pattern for Modal (mount with active={false}, then switch to active={true} via useEffect) because in the past focus trap didn't work correctly when Modal was mounted with active={true} directly. This issue might already be fixed, but even with two-phase activation the scroll jump shouldn't happen.

Bug: When opening a DropdownMenu inside a scrollable Modal that uses two-phase activation, iOS Safari scrolls the modal content to the top.

Reproduction: https://codesandbox.io/p/sandbox/muddy-leaf-kgr6r6
Steps to reproduce (iOS Safari only):

1. Open the modal
2. Scroll down
3. Tap a DropdownMenu trigger
4. Modal jumps to the top

Expected: Modal stays at the same scroll position

[blvdmitry]

I've just tried the same sandbox with the latest canary and it seems to be working fine there while I was able to reproduce with 3.9.0. I've made a refactor of how flyouts work in one of the canary releases so I'm guessing it solved this edge case too (I used 3.10.0-canary.16). I'm planning to release 3.10.0 once I resolve a few more tickets from the backlog planned for the minor release