fix(focusTrap): prevent page scroll when capturing focus in overlay

[jlee038]

Description

fixes #22802

When captureFocus redirects focus into an overlay's content element, focus() was called without { preventScroll: true }. If the overlay has not yet been positioned by updateLocation (ResizeObserver, async), the content element is at its default position (top: 0), causing the browser to scroll the page to the top to bring the focused element into view.

This is most visible when transition is disabled (:transition="false"), because the default VDialogTransition sets visibility: hidden during the enter animation which normally prevents the browser from scrolling to a hidden element — masking the bug.

The fix adds { preventScroll: true } to all three focus() calls in useFocusTrap because focus trap redirections shouldn't cause unintended page scroll. Intentional scrolls are handled elsewhere (e.g. scrollToIndex(), scrollIntoView()).

Markup:

<template>
  <v-app>
    <v-main>
      <v-container>
        <p v-for="n in 50" :key="n" class="my-1">Filler line {{ n }}</p>

        <div class="d-flex flex-column ga-3">
          <v-select
            v-for="n in 3"
            :key="n"
            v-model="vals[n - 1]"
            :items="items"
            :label="`Select ${n} — first time opening will scroll to top`"
            :transition="false"
            density="compact"
            variant="outlined"
            hide-details
          />
        </div>

        <p v-for="n in 10" :key="`b${n}`" class="my-1">Content below {{ n }}</p>
      </v-container>
    </v-main>
  </v-app>
</template>

<script setup>
  import { ref } from 'vue'

  const vals = ref([null, null, null])
  const items = ['Option A', 'Option B', 'Option C', 'Option D', 'Option E']
</script>

<style>
html,
body,
.v-application,
.v-main {
  overflow: visible !important;
  height: auto !important;
}
</style>