- Rewrite fitToCanvas to build the blurred story background with Imagick: scale the image to fill the width, heavily gaussian-blur it so shapes dissolve into a colour wash, gamma-lighten it, and mirror the top half onto the bottom for a symmetric background; the foreground is contained (fills the width, never cropped). Falls back to a GD downscale-blur on hosts without ext-imagick.
- Clean up the fit temp file if the blur/encode step throws.
- Update the editor preview (VerticalMediaCanvas) to a matching mirrored, lightened blur so it tracks the publish output.
- Cover the lightened image-derived background, the vertical mirror, and the GD fallback path with unit tests.
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