Add native-extension knowledge entries for cgo, Cython, pybind11/nanobind, scikit-build-core, cffi, SWIG, elixir_make, and the `cc` crate

[andrew]

Running 0.11.0 across ~22k repos, ~1,700 have C or C++ in languages[]. brief reports a native_extension or C build tool for roughly half; the rest fall into the bridges below. Each is the C/C++ analogue of the Rust bridges (maturin, napi-rs, rb-sys, rustler) that already have entries.

• cgo (knowledge/go/cgo.toml): [detect.file_contains] "*.go" = ['import "C"']. Evidence: https://github.com/go-gl/glfw (69,628 C loc, no tool reported), https://github.com/mattn/go-sqlite3, https://github.com/golang/snappy.
• Cython (knowledge/python/cython.toml): [detect.file_glob] = ["**/*.pyx"] and [detect.file_contains] "setup.py" = ["cythonize("]. Also add .pyx/.pxd to the language extension map so languages[] matches scc's Cython count. Evidence: https://github.com/numpy/numpy (13,387 .pyx loc), https://github.com/pandas-dev/pandas (43,386), https://github.com/aio-libs/yarl (Cython-only extension, brief currently reports languages: [Python]).
• pybind11 (knowledge/python/pybind11.toml): [detect.file_contains] "CMakeLists.txt" = ["pybind11_add_module", "find_package(pybind11"], "pyproject.toml" = ['"pybind11"'], "*.cpp" = ["#include <pybind11/"]. Evidence: https://github.com/pybind/pybind11, https://github.com/google/re2 python/, https://github.com/scipy/scipy.
• nanobind (knowledge/python/nanobind.toml): as pybind11 with nanobind. Evidence: https://github.com/google/flax flaxlib_src/ (requires = ["nanobind >=1.3.2"], #include <nanobind/nanobind.h>).
• scikit-build-core (knowledge/python/scikit-build-core.toml): [detect.file_contains] "pyproject.toml" = ['build-backend = "scikit_build_core']. Same shape as meson-python.toml from Add meson-python as a native_extension bridge #137. Evidence: https://github.com/google/flax flaxlib_src/.
• cffi (knowledge/python/cffi.toml): [detect.file_contains] "setup.py" = ["cffi_modules="]. Evidence: https://github.com/python-cffi/cffi.
• SWIG (knowledge/_shared/swig.toml): [detect.file_contains] "*.i" = ["%module "] (a bare **/*.i glob also matches preprocessor output). Also add .i to the language extension map so languages[] matches scc's Swig count. Evidence: https://github.com/mhammond/pywin32 (33,645 .i loc), https://github.com/libgdx/libgdx, https://github.com/lightgbm-org/lightgbm.
• elixir_make (knowledge/elixir/elixir_make.toml): [detect.file_contains] "mix.exs" = [":elixir_make", "compilers: [:elixir_make"]. C-NIF analogue of rustler.toml. Evidence: https://github.com/elixir-sqlite/exqlite.
• cc crate (knowledge/rust/cc.toml): [detect.file_contains] "Cargo.toml" = ["\ncc = ", "\ncc.workspace"]. 122 of 2,909 top crates.io repos have cc as a direct build-dependency; only 45 currently get any C build-tool signal. Evidence: https://github.com/briansmith/ring, https://github.com/BLAKE3-team/BLAKE3, https://github.com/dtolnay/cxx, https://github.com/FillZpp/sys-info-rs.
• node-addon-api / prebuild-install / prebuildify (knowledge/node/*.toml): [detect.dependencies] = ["node-addon-api"] etc. node-gyp.toml already covers binding.gyp; these separate "compiles on install" from "downloads a prebuilt .node". Evidence: https://github.com/lovell/sharp (all three).