fix(build): stop stripping zeroconf/_services + add import smoke test

- build-common.sh: remove zeroconf/_services from the strip list.
  zeroconf's compiled Cython _listener.pyd imports from _services
  internally, so stripping it broke `import zeroconf` at runtime with
  ModuleNotFoundError — same class of bug as the numpy.linalg strip.
- build-common.sh: add smoke_test_imports() that imports every top-level
  dependency against the stripped site-packages. Catches "we stripped
  something that was actually needed" regressions at build time instead
  of on a user's machine after install.
- build-dist.sh: wire smoke test into the Linux flow (runs real imports).
- build-dist-windows.sh: cross-build can't load win_amd64 .pyd files with
  the host python, so instead verify that the known-required submodule
  dirs (numpy.linalg/lib/matrixlib/ma, zeroconf._services) exist after
  cleanup. Fails loud if any future strip-rule removes them.

build-dist-windows.sh

@@ -279,6 +279,21 @@ find "$SITE_PACKAGES/winrt" -name "*.pyi" -delete 2>/dev/null || true
 # the generated .pyc will ImportError on the target.
 compile_and_strip_sources "$SITE_PACKAGES" "python"
 
+# Windows cross-build: host python can't load win_amd64 .pyd files, so
+# we can't `import numpy` for real. Instead, check that the submodules
+# known to be imported internally exist on disk — the same landmines that
+# cost users a broken v0.0.0.dev0 installer.
+echo "  Verifying required submodules exist after cleanup..."
+for required in \
+    "numpy/linalg" "numpy/lib" "numpy/matrixlib" "numpy/ma" \
+    "zeroconf/_services"; do
+    if [ ! -d "$SITE_PACKAGES/$required" ] && [ ! -f "$SITE_PACKAGES/$required.py" ] && [ ! -f "$SITE_PACKAGES/$required.pyc" ]; then
+        echo "  ERROR: $required missing from site-packages — cleanup_site_packages removed something required. Aborting."
+        exit 1
+    fi
+done
+echo "  All required submodules present."
+
 WHEEL_COUNT=$(ls "$WHEEL_DIR"/*.whl 2>/dev/null | wc -l)
 echo "  Installed $WHEEL_COUNT packages"