/* Build CTO surfaces: borders, radii, elevation, grid texture.
   Radius is 0 everywhere — the kinship rule. Flat by default; only overlays cast shadow. */
:root{
  --radius-0:0; /* never round */
  --border-hair:1px solid var(--border-hairline);
  --border-interactive:1px solid var(--border-strong);
  --shadow-none:none;
  --shadow-overlay:0 12px 32px rgba(22,22,19,.16); /* dialogs, toasts, dropdowns only */

  /* engineering grid texture — pair the image with background-size:var(--bc-unit) var(--bc-unit) */
  --grid-lines-on-ink:linear-gradient(rgba(245,245,240,.055) 1px,transparent 1px),linear-gradient(90deg,rgba(245,245,240,.055) 1px,transparent 1px); /* @kind other */
  --grid-lines-on-paper:linear-gradient(rgba(22,22,19,.045) 1px,transparent 1px),linear-gradient(90deg,rgba(22,22,19,.045) 1px,transparent 1px); /* @kind other */
}