fix: validate social preview metadata

tests/unit/metadata.test.ts

@@ -96,6 +96,30 @@ describe('safe metadata', () => {
     });
   });
 
+  it.each([
+    { name: 'audio', mediaType: 'audio/mpeg' as const, fileName: 'project-social-preview.mp3', width: null, height: null, durationMs: 1000 },
+    { name: 'video', mediaType: 'video/mp4' as const, fileName: 'project-social-preview.mp4', width: 1200, height: 630, durationMs: 1000 },
+    { name: 'vector image', mediaType: 'image/svg+xml' as const, fileName: 'project-social-preview.svg', width: 1200, height: 630, durationMs: null },
+    { name: 'wrong-size raster', mediaType: 'image/webp' as const, fileName: 'project-social-preview.webp', width: 1199, height: 630, durationMs: null },
+  ])('falls back to a summary card when the configured preview is $name', ({ mediaType, fileName, width, height, durationMs }) => {
+    const unsafeManifest = structuredClone(manifest);
+    const previewAsset = unsafeManifest.assets.find(({ id }) => id === content.metadata.socialPreviewAssetId)!;
+    previewAsset.mediaType = mediaType;
+    previewAsset.fileName = fileName;
+    previewAsset.width = width;
+    previewAsset.height = height;
+    previewAsset.durationMs = durationMs;
+
+    const metadata = createPageMetadata(content, unsafeManifest, productionSite);
+
+    expect(metadata.openGraph).not.toHaveProperty('image');
+    expect(metadata.twitter).toEqual({
+      card: 'summary',
+      title: 'Luca Pîslaru — System Administrator & Full-Stack Developer',
+      description: content.metadata.description,
+    });
+  });
+
   it('omits sameAs when no verified social profiles exist', () => {
     const withoutSocial = structuredClone(content);
     withoutSocial.contact.social = [];