test: add import smoke test (reveals undeclared selenium dep)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_imports.py

@@ -0,0 +1,32 @@
+import importlib
+import pkgutil
+
+import smileyface
+
+
+def test_top_level_package_imports():
+    importlib.import_module("smileyface")
+
+
+def test_all_submodules_import():
+    errors = []
+
+    def _on_walk_error(name):
+        errors.append(f"{name}: failed during package walk")
+
+    module_names = [
+        info.name
+        for info in pkgutil.walk_packages(
+            smileyface.__path__,
+            prefix="smileyface.",
+            onerror=_on_walk_error,
+        )
+    ]
+
+    for name in module_names:
+        try:
+            importlib.import_module(name)
+        except Exception as exc:  # noqa: BLE001 - we want every failure, not the first
+            errors.append(f"{name}: {exc!r}")
+
+    assert not errors, "Modules failed to import:\n" + "\n".join(errors)