10C Inc 3 + 4: I/O and text — the app's whole OCP surface is bound

138/138 symbols across 53 modules. New: IFSelect, Interface, XSControl,
IGESData, STEPControl, IGESControl, RWStl, Graphic3d, NCollection, StdPrs.

**The full app suite passes against this wheel: 1797 passed, 1 skipped — the
same result as the stock wheel**, run from the parity venv.

Getting there needed six methods that no static analysis could have found:
`inventory --check` only sees symbols reached through an import, so a method
called on an instance is invisible to it. The suite found them in one pass, and
one of them (gp_Vec.Reverse, which every outward-normal probe calls) accounted
for 311 of the 255 failing tests on its own. The others: gp_Trsf.SetMirror over
a plane and a point, Geom_Surface.D0, BRep_Builder.MakeFace from a
triangulation, MakePipeShell.SetMode with a fixed binormal, and MakeFace from a
surface plus tolerance.

Open question **S5 is settled: no**. The wheel does not need OCCT's share/
resources. test_inc3_io.py asserts no CSF_* variable is set and then round-trips
STEP and IGES, reading the declared units back off both — which is exactly the
resource-less container the question was about.

The XSTEP readers keep the GIL, amending the blanket "file readers and writers"
line in design.md's GIL policy. STEP and IGES traffic in process-global
Interface_Static state, the IGES reader is documented as not thread-safe, and
the app already serialises imports behind a lock — so holding it costs nothing
and removes a class of question. RWStl, which touches no global state, releases.

XSControl_Reader and IGESData are registered although the app imports neither:
they are the reader base both concrete readers inherit their transfer surface
from, and the model-to-global-section chain the IGES unit probe walks.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DfriM8XUkn7uYf5Dwe2xo6

pyproject.toml

@@ -9,7 +9,7 @@ name = "n3xd-ocp"
 # .devN suffix: the registry never allows republishing a version, and its
 # cleanup rule collects only the dev ones.  CMake asserts the prefix matches
 # the OCCT it found.
-version = "7.9.3.1.dev3"
+version = "7.9.3.1.dev4"
 description = "nanobind bindings for the OpenCASCADE geometry kernel (drop-in OCP)"
 readme = "README.md"
 requires-python = ">=3.12"