Plan step 36. The old `state-layer` utility hid its layer on
`[aria-disabled='true']`; the menu item's hand-written layer dropped
that, so a disabled item, which stays focusable, drew the 10% focus
layer. Its 38% ink now reads --md-sys-state-disabled-content-opacity,
as button.css does, instead of a literal.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9