Chore: Make the sample duplicate guard fail on a missing tree

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/documents/tests/test_sample_files.py

@@ -39,7 +39,6 @@ def test_install_uses_the_shared_bytes(tmp_path: Path) -> None:
 APP_SAMPLE_TREES = [
     Path(__file__).parent / "samples",
     Path(__file__).parents[2] / "paperless" / "tests" / "samples",
-    Path(__file__).parent / "examples",
     SHARED_SAMPLES_DIR,
 ]
 
@@ -47,9 +46,12 @@ APP_SAMPLE_TREES = [
 def test_no_two_sample_files_have_identical_bytes() -> None:
     by_hash: dict[str, list[Path]] = defaultdict(list)
     for tree in APP_SAMPLE_TREES:
+        assert tree.is_dir(), f"Sample tree does not exist: {tree}"
         for path in tree.rglob("*"):
-            if path.is_file():
+            # Skip empty placeholders, which would all hash identically
+            if path.is_file() and path.stat().st_size > 0:
                 by_hash[_sha(path)].append(path)
+    assert by_hash, "No sample files were found to compare"
     duplicates = {h: ps for h, ps in by_hash.items() if len(ps) > 1}
     lines = ["  " + ", ".join(str(p) for p in ps) for ps in duplicates.values()]
     message = (