Hairline-bordered panel with square corners and no shadow — the blueprint-frame convention. Optional header strip carries a mono label and a FIG./file tag.

```jsx
<Card label="EdisonSat — AI-MicroSat" fig="FIG. 01">
  <img src="assets/blueprint-sat.png" alt="" />
</Card>
<Card surface="ink" label="Spec" fig="Output">…</Card>
```

`surface="paper"` is the default inset bone panel; `surface="ink"` inverts to a dark panel (used for spec tables). Depth comes from the border, never a shadow.
