chore: ruff lint 修复 + 第一优先级全部完成

tests/test_splitters_pdf.py

@@ -1,6 +1,6 @@
 """PDFSplitter 测试."""
+
 import pytest
-from pathlib import Path
 
 pymupdf = pytest.importorskip("fitz", reason="pymupdf 未安装")
 
@@ -10,9 +10,10 @@ class TestPDFSplitter:
 
     def test_split_simple_pdf(self, tmp_path):
         """用 pymupdf 创建一个简单 PDF 并测试分块."""
-        from src.core.splitters.pdf import PDFSplitter
         import fitz
 
+        from src.core.splitters.pdf import PDFSplitter
+
         pdf_path = tmp_path / "test.pdf"
         doc = fitz.open()
         # 插入纯 ASCII 文本避免 CJK 字体编码问题
@@ -29,9 +30,10 @@ class TestPDFSplitter:
 
     def test_empty_pdf(self, tmp_path):
         """空 PDF（有页但无文字）返回空列表."""
-        from src.core.splitters.pdf import PDFSplitter
         import fitz
 
+        from src.core.splitters.pdf import PDFSplitter
+
         pdf_path = tmp_path / "empty.pdf"
         doc = fitz.open()
         doc.new_page()  # pymupdf 必须有至少一页才能保存