[stack] refactor(core): finalize migration to Vue 3 - #64998

The external share entry renders its menu entry and dialog as two roots
now instead of through vue-frag, and hands the attributes of the menu on
to the entry. The dialog reports when it closes, so the entry can open it
again and a spawned dialog is cleaned up.

The menus take the place of their placeholders like the header menus, as
their root carries the id of the placeholder. A primary action with a link
is a link for assistive technologies now, so the page object accepts both.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>
Assisted-by: ClaudeCode:claude-opus-5-5

The external filter store is a typed setup store. Its pinia instance is
active from the start, so `OCA.UnifiedSearch.registerFilterAction` keeps
working for apps that register a filter before the search is mounted.

The search view and the small result components use `<script setup>`, and
the events that Vue 2 forced into kebab-case are camelCase again. The
people filter and the custom date range follow the popover and modal of
nextcloud-vue 9 through v-model, as their show and hide events are gone.

The specs use the Vue 3 test utils: stubs expose what the view calls on
its children, and the selected row is compared against the raw focus trap.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>
Assisted-by: ClaudeCode:claude-opus-5-5

The legacy unified search uses `<script setup>`: the results, cursors and
limits per provider are plain reactive records, so `$set` and `$delete` are
gone, and the results forward their native events to the list instead of
re-emitting them. The keyboard listener is removed again when the search
unmounts, and requests are cancelled through an AbortController.

The search field is focused when the menu opens, a frame after
nextcloud-vue 9 reports it as opened: its content is not visible, and
thus not focusable, before.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>
Assisted-by: ClaudeCode:claude-opus-5-5