blank: fix keyboard z-coords for new base position + thinner lid panel
- Keyboard keys now on base z: 0 to 2*hd (was -hd to +hd)
- Lid thickness reduced to 0.9x hh (was 1.4x) — flatter display panel
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>