Composer gradient leaks into body instead of staying on animated border

[pathscale]

Symptom

The composer body is painted with a visible purple/blue gradient. The interior should be a normal flat surface colour; only the border should carry the animated treatment.

Required outcome

• Composer interior is a single flat authored colour.
• Animated gradient is clipped/masked to the border only.
• The result is correct in the Blitz renderer, not merely a browser.
• Add native ps-qa coverage that distinguishes the flat body from the animated border. A check that only proves some animation or gradient exists is insufficient.

Screenshot

Owner supplied Screenshot 2026-08-29 at 02.51.25.png.

Diagnostic clue

This looks like border-gradient clipping/masking or pseudo-element composition falling back incorrectly in Blitz. Audit recent composer and renderer changes and fix at the lowest shared layer proven responsible.