Replace onMount+onCleanup with createEffect watching ctx.isOpen() and
ctx.modal(), so focusTrap/scrollLock/dismiss activate/deactivate
reactively on every open/close — including when forceMount keeps the
component mounted.
Note: role="dialog" was omitted; the project's Biome rules flag it as
redundant (noRedundantRoles) since <dialog> carries the implicit role.