Plan step 19, containment.md C-12 and C-25. `padding` defaulted to 0 where M3's specs table gives every layout 16dp of leading and trailing padding — leading only for `uncontained`, none for the edge-to-edge `full-screen` — so the default is 16 and each layout now says which ends it applies to (`data-padding`, `data-padding-end`). The row gains the 8dp above and below that goes with it, without shortening the items. The overlay label is `inverse-on-surface` instead of a literal `white`, which no scheme or contrast profile follows. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9