Plan step 12, containment.md C-05. Only the parallax half of M3's rule was honoured: the mask was still written every frame, so items kept growing and shrinking between the keylines. Under reduced motion the inset, the shift and the label fade are now all zero, so every item stays at the strategy's large size and the keylines only decide where the row snaps. `--material-carousel-pin` went with it: with no mask there is nothing to pin the content to. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9