fix: use context managers for file handles to prevent resource leaks (#13514)

## Summary
- Convert bare `open()` calls to `with` context managers or
`Path.read_text()`
- File handles leak if not properly closed, especially on exceptions
- Fixes in crypt.py, sequence2txt_model.py, term_weight.py,
deepdoc/vision/__init__.py

## Test plan
- [x] File operations work correctly with context managers
- [x] Resources properly cleaned up on exceptions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

deepdoc/vision/__init__.py

@@ -60,9 +60,8 @@ def init_in_out(args):
             pdf_pages(fnm)
             return
         try:
-            fp = open(fnm, "rb")
-            binary = fp.read()
-            fp.close()
+            with open(fnm, "rb") as fp:
+                binary = fp.read()
             images.append(Image.open(io.BytesIO(binary)).convert("RGB"))
             outputs.append(os.path.split(fnm)[-1])
         except Exception: