fix(Dialog,AlertDialog): omit aria-labelledby/describedby when title/description absent

[sridhar-3009]

Problem

DialogContent and AlertDialogContent unconditionally emit aria-labelledby={titleId} and aria-describedby={descriptionId} even when DialogTitle / DialogDescription are not rendered. If the referenced element doesn't exist in the DOM, the IDREF is dangling — invalid per the ARIA spec. Screen readers may announce empty text or skip the dialog's accessible name.

Closes #608.

Solution

Presence-track Title and Description sub-components using ShallowRef<boolean> in the root context, set/unset via onMounted/onUnmounted. Content components then gate the ARIA attributes on whether the sub-component is actually present:

'aria-labelledby': context.titlePresent.value ? context.titleId : undefined,
'aria-describedby': context.descriptionPresent.value ? context.descriptionId : undefined,

Files changed: DialogRoot.vue, DialogTitle.vue, DialogDescription.vue, DialogContent.vue, AlertDialogRoot.vue, AlertDialogTitle.vue, AlertDialogDescription.vue, AlertDialogContent.vue.

[github-actions]

✅ Changeset found — this change will be included in the next release. Thanks!