[Bug] MobileNav: closing the drawer skips the slide out animation

### Description

When closing MobileNav on mobile, the drawer disappears instantly instead of sliding out. Opening works fine and animates smoothly, but closing has no visible transition at all.

Would be good to get eyes on this since MobileNav's animation is being referenced as the model pattern in #4174.

### Reproduction

1. Open the mobile nav drawer (opening is animated correctly)
2. Close it via backdrop click, close button, or Escape
3. Drawer vanishes immediately, no animation

Example is available at the playground [here](https://astryx.atmeta.com/playground#code=lVVtT9swEP7eX3HqNBWkisCG-AApGmOairQNpMK-u_E18ebYxXZYuyr_fee81alYgUqV4rt77p57cr6MCouQSIHKjS4GA5EvtXGwuVouZxlKWcLC6BxGn5h1Zr3iaEWqokQbjNoQgrWonzPHkt97MJU_AEyRcaHSMdzjyu3BeXcA-8GebhKt9gCaiAAzAJgJjuQYbx_b-lvLjcM8OM4wcUKr8WBfU3Vov9Z1xoz7zIxn4fN91ZJjd3qwaGx7uNbp2b3WLqsNXaUMjRZkspFBlrjow2mkCyeFwlBBnWNPi2dQVkvBA8x1MX8Rs600wFUF47hghXSwKFSlCbQD0PR_q-T64LBq3qArjIIDegSI27jqBEB1HE3bHeNe-snmrGwc1q0lTjabDEWauXMYnRwfvx-NIRdq2piOyy64Ljrx5epf3PDoDAAZvV40QUwY17z7ng_Ay7ADqEDNQDX-uJWwI_1HcJedw8nZmKrWZE_OyhKiS__fydc2EfL0WgxJKqi0Gj4fMTW4mAzf9b299GV4aFttphiccER2-J0JNQRhvQJopoJzVH2KLdDfhh0mks1RToZfmM3mmhm-y7QWqBvLXa-doSQ2yHcbfLGzPquWx5Vicu1EYqmhqnJ48cou7WtS3Rn9i6h1mbZX9n954vbuNwK_QvtbkzIl_jJvG77M6R5Z3vLplsbb2pqhczQ6W4HCdfP2zjpPa-omLq7XP6RsOdmcBoMYN1cNJD4Ro83H8vKOpUiLr9oEcdT4A4Rf-ODWS1Jsrvm6p9Q3Wro5iKUtcuBaakPLwAHL0Y39crF-vGj_AOVcCpv4wiiFO4IZcgIEmVAUNtccSC1acSBUIrjghXJQOC8fFQKkzeeLIOQsVQyYFI8FO4IHB6hETlWChLSqyPREDpaP4bEQFpSmD0bBAVdoEuGqFw-FlCxPdF1D2KNAXd95p2hUS1qf4-6T68-HF4Ny8A8)
Its the second example from the [docs](https://astryx.atmeta.com/components/AppShell)

### Astryx Version

@astryxdesign/core@0.5.2

### Environment

_No response_

Start at the MobileNav component and reproduce the issue using the linked playground or the second AppShell docs example. Trace the close paths for backdrop clicks, the close button, and Escape, then verify that each preserves the drawer's slide-out animation before it disappears.

Written by the indexing model from the issue text.