fix(ci): place NVX .so at wheel root and fix PyPy ARM64 build

Two fixes for CI failures:

1. hatch_build.py: Place NVX .so files at WHEEL ROOT (not autobahn/nvx/)
   - CFFI creates top-level modules (e.g., "_nvx_utf8validator")
   - Python imports them as `import _nvx_utf8validator` (top-level)
   - When installed from wheel, the .so must be in site-packages root
   - This fixes: "RuntimeError: NVX native acceleration explicitly
     requested via AUTOBAHN_USE_NVX=1, but NVX modules are not available"

2. build-arm64-wheel.sh: Disable py-ubjson C extension for PyPy on ARM64
   - The C extension segfaults (exit -11) under QEMU ARM64 emulation
   - py-ubjson works fine as pure Python under PyPy's JIT
   - Sets PYUBJSON_NO_EXTENSION=1 when building for PyPy

Note: This work was completed with AI assistance (Claude Code).

Author: oberstet

.github/scripts/build-arm64-wheel.sh

@@ -50,6 +50,14 @@ echo "auditwheel: $(auditwheel --version || echo 'not available')"
 # nh3 is a Rust package (indirect dep of twine) that segfaults under QEMU
 export AUTOBAHN_USE_NVX=1
 
+# Disable py-ubjson C extension for PyPy on ARM64
+# The C extension build segfaults under QEMU ARM64 emulation (exit code -11)
+# py-ubjson works fine as pure Python under PyPy's JIT
+if python3 -c "import platform; exit(0 if 'pypy' in platform.python_implementation().lower() else 1)" 2>/dev/null; then
+  echo "==> PyPy detected: disabling py-ubjson C extension (QEMU ARM64 incompatible)"
+  export PYUBJSON_NO_EXTENSION=1
+fi
+
 # Build only specified Python versions (or all if not specified)
 if [ -n "$PYTHON_VERSIONS" ]; then
   echo "==> Building wheels for specific Python versions: $PYTHON_VERSIONS"

hatch_build.py

@@ -110,22 +110,18 @@ def _build_cffi_modules(self, build_data):
 
                 # Find the compiled artifact matching CURRENT Python and add to build_data
                 # Only include .so files that match the current interpreter's extension suffix
+                #
+                # IMPORTANT: The .so files must be placed at the WHEEL ROOT (not in autobahn/nvx/)
+                # because CFFI creates top-level modules (e.g., "_nvx_utf8validator")
+                # and the Python code does `import _nvx_utf8validator` (top-level import).
                 for artifact in nvx_dir.glob("_nvx_*" + ext_suffix):
                     src_file = str(artifact)
-                    dest_path = f"autobahn/nvx/{artifact.name}"
+                    # Place at wheel root for top-level import
+                    dest_path = artifact.name
                     build_data["force_include"][src_file] = dest_path
-                    print(f"  -> Added artifact: {artifact.name} -> {dest_path}")
+                    print(f"  -> Added artifact: {artifact.name} -> {dest_path} (wheel root)")
                     built_any = True
 
-                # Handle Windows .pyd files
-                if ext_suffix.endswith(".pyd"):
-                    for artifact in nvx_dir.glob("_nvx_*" + ext_suffix):
-                        src_file = str(artifact)
-                        dest_path = f"autobahn/nvx/{artifact.name}"
-                        build_data["force_include"][src_file] = dest_path
-                        print(f"  -> Added artifact: {artifact.name} -> {dest_path}")
-                        built_any = True
-
             except Exception as e:
                 print(f"Warning: Could not build {module_file}: {e}")
                 import traceback