Add bulk UV sampler, TKHelix and MakeSphere (8.0.1.2)

- n3xd_ocp.sample.face_grid: a face's UV grid of points and outward
  normals in one GIL-free call, sampling exactly where np.linspace does
  so a caller's fitted surface does not move.
- n3xd_ocp.helix: OCCT 8.0's TKHelix, which upstream does not bind at
  all. Takes Python lists rather than NCollection_Array1. Two things the
  header does not say, both found by probing: SetParameters wants N+1
  diameters for N segments (one per boundary, so a taper interpolates),
  and the builder is right-hand only -- a negative pitch is error status
  12, not a mirrored helix.
- Bind BRepPrimAPI_MakeSphere and give inventory.py an EXTRA_SYMBOLS
  addendum for symbols no app source imports. assay's gen_flow_fixtures
  has been unrunnable since the 10C cutover for want of it; the gap was
  wider than --check, since sigdiff is inventory-driven too.

Gates: 105 tests, 139/139 symbols, sigdiff clean, ASAN clean, wheel
self-contained with no libGL/libX11 DT_NEEDED.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HbTQ2HYWQwdtGmGJwypt6Z

python/n3xd_ocp/__init__.py

@@ -16,8 +16,10 @@ import sys
 import OCP as _OCP_pkg  # noqa: F401  (loads the extension, registering us)
 
 bintools = sys.modules["n3xd_ocp.bintools"]
+helix = sys.modules["n3xd_ocp.helix"]
 measure = sys.modules["n3xd_ocp.measure"]
+sample = sys.modules["n3xd_ocp.sample"]
 tess = sys.modules["n3xd_ocp.tess"]
 _debug = sys.modules["n3xd_ocp._debug"]
 
-__all__ = ["bintools", "measure", "tess"]
+__all__ = ["bintools", "helix", "measure", "sample", "tess"]