[refactor] Rename ResultGallery to MediaLightbox and address code review (#10235)

## Summary
Address code review feedback from #10134 by renaming the component and
improving implementation quality.

## Changes
- Rename `ResultGallery` → `MediaLightbox` across all references
- Replace `useEventListener(window, 'keydown')` with `@keydown` on
dialog element
- Remove change detector tests (`renders close button`, `prevents
default on arrow keys`)
- Remove redundant `toBeVisible()` before Playwright click (implicit
wait)
- Update keyboard tests to dispatch on dialog element instead of
`window`
- Sort button icon sizes (`icon-sm`, `icon`, `icon-lg`)
- Wire zoom event to lightbox in `MediaAssetCard` story via
`context.args`
- Add standalone `MediaLightbox` Storybook story under
`Platform/Assets/`

Fixes #10134

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10235-refactor-Rename-ResultGallery-to-MediaLightbox-and-address-code-review-3276d73d365081299b42f682373a12f1)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: Amp <amp@ampcode.com>

src/components/sidebar/tabs/AssetsSidebarTab.vue

@@ -170,7 +170,7 @@
       </div>
     </template>
   </SidebarTabTemplate>
-  <ResultGallery
+  <MediaLightbox
     v-model:active-index="galleryActiveIndex"
     :all-gallery-items="galleryItems"
   />
@@ -220,7 +220,7 @@ import AssetsSidebarGridView from '@/components/sidebar/tabs/AssetsSidebarGridVi
 import AssetsSidebarListView from '@/components/sidebar/tabs/AssetsSidebarListView.vue'
 import SidebarTabTemplate from '@/components/sidebar/tabs/SidebarTabTemplate.vue'
 import Skeleton from '@/components/ui/skeleton/Skeleton.vue'
-import ResultGallery from '@/components/sidebar/tabs/queue/ResultGallery.vue'
+import MediaLightbox from '@/components/sidebar/tabs/queue/MediaLightbox.vue'
 import Tab from '@/components/tab/Tab.vue'
 import TabList from '@/components/tab/TabList.vue'
 import Button from '@/components/ui/button/Button.vue'