chore: import upstream snapshot with attribution

tests/cli/test_kb_cli.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from deeptutor_cli.kb import _collect_documents
+
+
+def test_collect_documents_from_directory_matches_uppercase_extensions(tmp_path: Path) -> None:
+    docs_dir = tmp_path / "资料"
+    docs_dir.mkdir()
+    upper_pdf = docs_dir / "报告.PDF"
+    upper_pdf.write_bytes(b"%PDF-1.4")
+    nested = docs_dir / "nested"
+    nested.mkdir()
+    upper_md = nested / "README.MD"
+    upper_md.write_text("hello", encoding="utf-8")
+
+    collected = [Path(path).name for path in _collect_documents([], str(docs_dir))]
+
+    assert collected == ["README.MD", "报告.PDF"]