Dialog/Drawer backdrop is always mounted even with lazyMount and unmountOnExit

### Description When I use Dialog/Drawer component in Svelte and also using lazyMount and unmountOnExit I expected that backdrop and content are not mounted when not open, reality is that backdrop is always mounted, but the content works as expected. ### Link to Reproduction (or Detailed Explanation) https://stackblitz.com/edit/svelte-ark-ui-bug-dialog-1x124?file=src%2FApp.svelte ### Steps to Reproduce 1. Go to `https://stackblitz.com/edit/svelte-ark-ui-bug-dialog-1x124?file=src%2FApp.svelte` 2. Go to `App.svelte`, look for the lazyMount and unmountOnExit. 3. Open devtools to see the html. 4. Div with `data-part="backdrop"` is rendered, but it shouldn't ### Ark UI Version 5.20.0 ### Framework - [ ] React - [ ] Solid - [ ] Vue - [x] Svelte ### Browser Brave 1.87.191 (Official Build) (arm64) Chromium: 145.0.7632.120. But I think it occurs on all browsers ### Additional Information Briefly looked into the source, and the usePresence hook is used differently in backdrop compared to content components, maybe it would help