feat(builder): media package -- image crop/perf, video size+picker, gallery cols/lightbox, box-model+anim/vis rollout

- ImageBlock/ImageStylePanel: SizeControl width(absorbs old maxWidth
  presets)/height, AspectRatioControl + OBJECT_FIT grid + FocalPointGrid for
  CSS framing crop (aspect-ratio/object-fit/object-position on the <img>).
  Exported <img> always gets loading="lazy" decoding="async", plus width/
  height attrs when the style has a plain px length (pxAttr helper).
- VideoBlock/MediaStylePanel: Video URL text input replaced with
  AssetPicker(mediaType="video") writing videoUrl (paste-URL still handles
  YouTube/Vimeo, upload/browse handle files). Added SizeControl(width) +
  AspectRatioControl so the video frame honors real size/aspect instead of
  a hardcoded 16:9 (padding-bottom hack replaced with CSS aspect-ratio).
  New optional `poster` prop (image AssetPicker) + preload="metadata" on
  file-type <video>.
- Gallery: surfaced the existing-but-unexposed `columns` and `lightbox`
  props with panel controls.
- All 5 owned components (ImageBlock, VideoBlock, Gallery, ContentSlider,
  MapEmbed): added margin/padding (per-side)/border/box-shadow/opacity style
  defaults + AnimationControl/VisibilityControl-backed animation/
  animationDelay/hideOnDesktop/hideOnTablet/hideOnMobile props. New shared
  mediaBoxModel.tsx (package-local, not shared.tsx) DRYs the box-model +
  border/effects + animation/visibility panel sections across
  ImageStylePanel and MediaStylePanel.
- Tests: extended *.toHtml.test.ts for all 5 components (crop/perf attrs,
  video size/aspect/poster/preload, gallery columns/lightbox, box-model
  style emission, craft.props presence) + new MediaStylePanel.video.test.tsx
  verifying the AssetPicker wiring writes videoUrl/poster and the video-only
  size controls are gated on videoUrl. 694 tests green, tsc + vite build
  clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/components/media/ImageBlock.tsx

@@ -9,6 +9,23 @@ interface ImageBlockProps {
   src?: string;
   alt?: string;
   style?: CSSProperties;
+  animation?: string;
+  animationDelay?: string;
+  hideOnDesktop?: boolean;
+  hideOnTablet?: boolean;
+  hideOnMobile?: boolean;
+}
+
+/** Extracts the numeric portion of a plain "<n>px" CSS length string, for
+ *  emitting real `width`/`height` HTML attributes on the exported `<img>`
+ *  (helps the browser reserve layout space before the image loads --
+ *  avoiding CLS -- something a CSS-only width/height can't do on its own).
+ *  Returns undefined for any other unit ('%', 'auto', '', etc.) so the
+ *  attribute is simply omitted when the pixel size isn't known. */
+export function pxAttr(v: unknown): string | undefined {
+  if (typeof v !== 'string') return undefined;
+  const m = v.trim().match(/^(\d+(?:\.\d+)?)px$/);
+  return m ? m[1] : undefined;
 }
 
 // Helper: upload a file to the WHP API and return the proxy URL
@@ -83,7 +100,27 @@ export const ImageBlock: UserComponent<ImageBlockProps> = ({
 
 ImageBlock.craft = {
   displayName: 'Image',
-  props: { src: PLACEHOLDER_SRC, alt: '', style: { width: '100%', height: 'auto' } },
+  props: {
+    src: PLACEHOLDER_SRC,
+    alt: '',
+    style: {
+      width: '100%',
+      height: 'auto',
+      aspectRatio: '',
+      objectFit: '' as CSSProperties['objectFit'],
+      objectPosition: '',
+      marginTop: '', marginRight: '', marginBottom: '', marginLeft: '',
+      paddingTop: '', paddingRight: '', paddingBottom: '', paddingLeft: '',
+      border: 'none',
+      boxShadow: 'none',
+      opacity: '1',
+    },
+    animation: '',
+    animationDelay: '0',
+    hideOnDesktop: false,
+    hideOnTablet: false,
+    hideOnMobile: false,
+  },
   rules: { canDrag: () => true, canMoveIn: () => false, canMoveOut: () => true },
 };
 
@@ -95,5 +132,8 @@ ImageBlock.craft = {
   }
   const s = cssPropsToString({ display: 'block', maxWidth: '100%', ...props.style });
   const alt = props.alt ? ` alt="${escapeAttr(props.alt)}"` : ' alt=""';
-  return { html: `<img src="${escapeAttr(safeImageUrl(src))}"${alt}${s ? ` style="${s}"` : ''} />` };
+  const widthAttr = pxAttr((props.style as any)?.width);
+  const heightAttr = pxAttr((props.style as any)?.height);
+  const dims = `${widthAttr ? ` width="${widthAttr}"` : ''}${heightAttr ? ` height="${heightAttr}"` : ''}`;
+  return { html: `<img src="${escapeAttr(safeImageUrl(src))}"${alt}${dims} loading="lazy" decoding="async"${s ? ` style="${s}"` : ''} />` };
 };