chore: import upstream snapshot with attribution

setup.py

@@ -0,0 +1,128 @@
+"""Build script for Cider.
+
+Usage:
+    pip install -e .          # Editable install (dev)
+    pip install .             # Regular install
+    python setup.py build_ext # Build C++ extension only
+
+The C++ extension is built via CMake and installed into cider/lib/.
+On Apple M4 and below, the C++ extension is skipped (INT8 TensorOps
+require M5+). The pure-Python package still installs and provides
+graceful fallback via is_available() → False.
+"""
+
+import os
+import platform
+import re
+import subprocess
+import sys
+from pathlib import Path
+
+from setuptools import setup, Extension
+from setuptools.command.build_ext import build_ext
+
+
+def _detect_apple_chip() -> int:
+    """Detect Apple Silicon generation. Returns chip number (4, 5, ...) or 0 if unknown."""
+    if platform.system() != "Darwin":
+        return 0
+    try:
+        brand = subprocess.run(
+            ["sysctl", "-n", "machdep.cpu.brand_string"],
+            capture_output=True, text=True, timeout=5
+        ).stdout.strip()
+        m = re.match(r"Apple M(\d+)", brand)
+        return int(m.group(1)) if m else 0
+    except Exception:
+        return 0
+
+
+def _should_build_ext() -> bool:
+    """Determine if C++ extension should be built."""
+    # Allow forcing via env var
+    force = os.environ.get("CIDER_FORCE_BUILD", "").lower()
+    if force in ("1", "true", "yes"):
+        return True
+    if force in ("0", "false", "no"):
+        return False
+    # Auto-detect: only build on M5+
+    chip = _detect_apple_chip()
+    if chip >= 5:
+        return True
+    if chip > 0:
+        print(f"[cider] Detected Apple M{chip} — skipping C++ extension (requires M5+)")
+        return False
+    # Unknown chip (cross-compile, CI, etc.) — try to build
+    return True
+
+
+class CMakeBuild(build_ext):
+    def build_extension(self, ext):
+        src_dir = Path(__file__).parent.resolve()
+
+        # Resolve paths that cmake can't find in pip's isolated build env
+        import sysconfig
+        python_include = sysconfig.get_path("include")
+
+        try:
+            import nanobind
+            nanobind_dir = nanobind.cmake_dir()
+        except ImportError:
+            nanobind_dir = ""
+
+        cmake_args = [
+            f"-DPython_EXECUTABLE={sys.executable}",
+            f"-DPython_INCLUDE_DIR={python_include}",
+            "-DCMAKE_BUILD_TYPE=Release",
+        ]
+        if nanobind_dir:
+            cmake_args.append(f"-Dnanobind_DIR={nanobind_dir}")
+
+        build_args = ["--config", "Release", "-j"]
+
+        # In-source build (cmake outputs .so to src_dir)
+        subprocess.check_call(
+            ["cmake", "."] + cmake_args,
+            cwd=src_dir,
+        )
+        subprocess.check_call(
+            ["cmake", "--build", "."] + build_args,
+            cwd=src_dir,
+        )
+
+        import shutil
+
+        # Copy .so to build_lib root (where setuptools expects the extension)
+        build_lib = Path(self.build_lib)
+        build_lib.mkdir(parents=True, exist_ok=True)
+        for f in src_dir.glob("_cider_prim*.so"):
+            shutil.copy2(f, build_lib)
+
+        # Also copy to cider/lib/ for runtime loading
+        output_lib_dir = build_lib / "cider" / "lib"
+        output_lib_dir.mkdir(parents=True, exist_ok=True)
+        for f in src_dir.glob("*.so"):
+            shutil.copy2(f, output_lib_dir)
+        for f in src_dir.glob("*.dylib"):
+            shutil.copy2(f, output_lib_dir)
+
+        # Write to source tree cider/lib/ so editable installs work
+        src_lib_dir = src_dir / "cider" / "lib"
+        src_lib_dir.mkdir(exist_ok=True)
+        for f in src_dir.glob("*.so"):
+            shutil.copy2(f, src_lib_dir)
+        for f in src_dir.glob("*.dylib"):
+            shutil.copy2(f, src_lib_dir)
+
+
+if _should_build_ext():
+    ext_modules = [Extension("_cider_prim", sources=[])]
+    cmdclass = {"build_ext": CMakeBuild}
+else:
+    ext_modules = []
+    cmdclass = {}
+
+setup(
+    ext_modules=ext_modules,
+    cmdclass=cmdclass,
+)