feat: make media inspection progressive

tests/unit/components/media-preview.test.tsx

@@ -43,7 +43,7 @@ describe('MediaPreview', () => {
     expect(progressiveVideo).toHaveAttribute('src', probingAsset.objectUrl);
     expect(
       screen.getByText(
-        'Local source preview · Media inspection continues in the background.'
+        'Local source preview · Detailed inspection runs separately.'
       )
     ).toBeVisible();
 
@@ -61,6 +61,64 @@ describe('MediaPreview', () => {
     expect(container.querySelector('video')).toBe(progressiveVideo);
   });
 
+  it('keeps browser playback mounted after detailed inspection fails', () => {
+    const asset: ImportedMediaAsset = {
+      id: 'asset-probe-error',
+      file: new File(['video'], 'lecture.mp4', { type: 'video/mp4' }),
+      objectUrl: 'blob:probe-error',
+      phase: 'error',
+      error: 'Detailed inspection timed out.',
+    };
+
+    const { container } = render(<MediaPreview asset={asset} />);
+
+    expect(container.querySelector('video')).toHaveAttribute(
+      'src',
+      asset.objectUrl
+    );
+    expect(
+      screen.getByText(
+        'Local source preview · Detailed inspection unavailable.'
+      )
+    ).toBeVisible();
+  });
+
+  it('keeps the video-container player when browser metadata has no track hints', () => {
+    const file = new File(['audio-only'], 'audio-only.mp4', {
+      type: 'video/mp4',
+    });
+    const initial: ImportedMediaAsset = {
+      id: 'asset-audio-only-container',
+      file,
+      objectUrl: 'blob:audio-only-container',
+      phase: 'idle',
+    };
+    const { container, rerender } = render(<MediaPreview asset={initial} />);
+    const player = requiredElement(container.querySelector('video'));
+
+    rerender(
+      <MediaPreview
+        asset={{
+          ...initial,
+          browserMetadata: {
+            source: 'browser',
+            file: {
+              name: file.name,
+              sizeBytes: file.size,
+              declaredMimeType: file.type,
+              inferredMimeType: file.type,
+              lastModified: file.lastModified,
+            },
+            kind: 'video',
+            durationSeconds: 8,
+          },
+        }}
+      />
+    );
+
+    expect(container.querySelector('video')).toBe(player);
+  });
+
   it('offers bounded configurable proxy settings after playback fails', async () => {
     const user = userEvent.setup();
     const onCreateProxy = vi.fn();