usd-brep library, specifically occt_to_usd conversion for NURBS-based boundary representation (BRep) solid modeling, with a focus on accurate area calculation for complex geometries.

### Summary

A single planar face imported with `occt_to_usd` comes back from `usd_brep` with an area about **0.65% too large**, and the error does **not** go away as `relative_accuracy` is tightened: it plateaus at +0.6525% from 1e-6 down to 1e-12. KNOWN_ISSUES.md ("Area, volume and mass properties of faces bounded by circles") says the error falls as the accuracy is tightened; here it stops falling well above zero, so that workaround does not apply.

The face's 3D boundary survives the round trip exactly. The extra area comes from the region SMLib treats as inside the trim.

### Environment

- usd-brep `c9c5979` (main, 2026-10-09), Windows 11, release build (VS 2022 Build Tools, v143 toolset)
- Input `.brep` written by OCCT 8.0 (via `cadquery-ocp` 8.0.1) in ASCII format V3

### Face

One planar face with one loop of 6 edges, all B-spline curves. The two long edges are rational with interior knots (weights around 0.9997 to 0.99985). The face comes from a vendor STEP model of a pre-cambered steel member. It was translated so its bbox min corner sits at the origin, and the error is the same before and after the translation.

### Reproduce

```
occt_to_usd face3149.brep face3149.usda
```

```python
import usd_brep.usd as ubu
face = ubu.import_breps("face3149.usda")[0].faces()[0]
for acc in (1e-1, 1e-3, 1e-6, 1e-9, 1e-12):
print(acc, face.area(acc))
```

### Measured

| Method | Area | vs reference |
|---|---|---|
| Reference: vector area of the closed boundary polyline (Gre...