test: smoke-test script for installed artifacts (catches the 0.2.2 import crash)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/smoke_import.py

@@ -0,0 +1,54 @@
+"""Smoke-test an *installed* app_skellington (wheel, sdist or index release).
+
+Run it from outside the source tree, so the installed copy is the one imported:
+
+    cd / && python /path/to/scripts/smoke_import.py [EXPECTED_VERSION]
+"""
+
+import importlib.metadata
+import os
+import pathlib
+import subprocess
+import sys
+
+
+def fail(msg):
+    sys.exit("smoke FAILED: " + msg)
+
+
+def main(argv):
+    expected = argv[1] if len(argv) > 1 else None
+
+    import app_skellington
+
+    location = pathlib.Path(app_skellington.__file__).resolve()
+    if "site-packages" not in location.parts:
+        fail("imported the source tree, not an installed copy: %s" % location)
+
+    from app_skellington import (  # noqa: F401  (the public API must import)
+        ApplicationContainer,
+        CommandTree,
+        Config,
+        LoggingLayer,
+        NoCommandSpecified,
+        ServiceNotFound,
+        SubMenu,
+    )
+
+    version = importlib.metadata.version("app_skellington")
+    if version.startswith("0.0"):
+        fail("setuptools_scm found no tags (shallow clone?): %s" % version)
+    if expected is not None and version != expected:
+        fail("expected version %s, got %s" % (expected, version))
+
+    # _bootstrap.py takes a different code path when APPSKELLINGTON_DEBUG is set.
+    env = dict(os.environ, APPSKELLINGTON_DEBUG="1")
+    proc = subprocess.run([sys.executable, "-c", "import app_skellington"], env=env)
+    if proc.returncode != 0:
+        fail("import failed with APPSKELLINGTON_DEBUG=1")
+
+    print("smoke ok:", version, location)
+
+
+if __name__ == "__main__":
+    main(sys.argv)