[NiJingzhe]

What

The geometry engine is now C++20 on OpenCASCADE (src/cpp), shipped inside the wheel as simplecadapi._cpp. One distribution, one import package. The public API and the previous Python test suite are unchanged: pytest test tests passes on the new engine.

• Layout: src/cpp and src/simplecadapi side by side. simplecadapi.core, .operators.*, .ql, .std.* ... are forwarding modules that name the C++ source of each name; the Python adapter layer is simplecadapi/_glue.
• OCP removed: cadquery-ocp, ocp-gordon, py-slvs are no longer dependencies; nothing imports OCP. shape.wrapped is the module's own binding, simplecadapi._cpp.occt.
• Prebuilt wheels (release workflow): Linux x86_64 and aarch64 (manylinux_2_28), macOS arm64 (14+), Windows x86_64; Python 3.10-3.13; one static OCCT 7.9.3 built by src/cpp/tools/build_occt.py. Publishes to GitHub and PyPI (last step, trusted publishing or PYPI_API_TOKEN). dry_run builds and verifies everything without publishing.
• Errors: every message the library writes is English; the tag-validation and semantic-query errors render in full with causes and fixes.
• Version: 2.2.7b1 (second commit: version, CHANGELOG, update notes EN/zh-CN, README).

arm6 benchmark (same sources, same machine): cold build 43.8 s -> 29.1 s, nothing changed 12.8 s -> 6.0 s, import simplecadapi 1.6 s / 360 MB -> 0.2 s / 68 MB; computed volumes agree to 1e-12.

Verified locally

• macOS arm64: pytest test tests 2114 passed, src/cpp/tests/python 460, ctest 14/14; a wheel built against the static OCCT installs in a clean venv, has no external library dependency, and passes the wheel smoke test.
• Linux aarch64: manylinux wheel built in the cibuildwheel container (static OCCT), repaired by auditwheel, smoke test passed.
• Python 3.10, 3.11, 3.12, 3.13: module built and full suite run.

Not verified yet

• Linux x86_64 and Windows wheels, and the release workflow on GitHub (no run yet). The checks of this PR are the first real Linux x86_64 build of the C++ module; run the release workflow with dry_run before tagging.
• One known numeric difference with the static OCCT: the bounding box upper bound of a point-constrained plate surface comes out 0.1% low (OCCT's AddOptimal is a heuristic optimiser); geometry, area and centre agree.

Before tagging

workflow_dispatch with dry_run, then tag v2.2.7b1. PyPI needs the trusted publisher registered for this workflow (environment pypi) or a PYPI_API_TOKEN secret.

Co-Authored-By: Claude Sonnet 5.5 noreply@anthropic.com