Fix/qa defects df002 df011 (#9)

## Summary

What changed and why?

## Change Type

- [ ] Cowork feature
- [ ] Bug fix
- [ ] Core AI contribution
- [ ] Test / hardening
- [ ] Performance
- [ ] Documentation

## Related Work

Cowork Task:

Core Repo: http://34.143.229.138/gitea-admin/fsg-ai-core-assets

Core AI Issue:

Core Task:

Related PR:

## Scope

What is intentionally included?

What is intentionally NOT included?

## Validation

- [ ] Unit tests
- [ ] Integration tests
- [ ] Manual verification
- [ ] Regression check

Commands / evidence:

## Security Impact

Permission / credential / network / customer data impact:

## Compatibility

- [ ] No breaking change
- [ ] Breaking change documented

## Reviewer Notes

Anything Cowork reviewers should pay attention to.

---------

Co-authored-by: thanhnv <thanhnv.ip@gmail.com>
Co-authored-by: Vu Dam Tuan <vudt15@fpt.com>
Reviewed-on: #9

core/ms365_graph.py

@@ -196,6 +196,40 @@ def write_onedrive_file(token: str, path: str, content: str) -> dict:
     return resp.json()
 
 
+# Graph's "simple upload" (a single PUT to .../content) is documented to only
+# support items up to 4 MiB; anything larger needs a chunked "upload session"
+# (createUploadSession + PUT-per-range), which this module does not implement
+# (see DF-007 cloud workspace picker — v1 explicitly skips large files rather
+# than silently truncating or corrupting them).
+MAX_SIMPLE_UPLOAD_BYTES = 4 * 1024 * 1024
+
+
+def _check_upload_size(data: bytes) -> None:
+    if len(data) > MAX_SIMPLE_UPLOAD_BYTES:
+        raise Ms365GraphError(
+            f"File too large for simple upload ({len(data)} bytes > "
+            f"{MAX_SIMPLE_UPLOAD_BYTES} bytes) — chunked upload sessions are not "
+            "implemented yet."
+        )
+
+
+def download_onedrive_file_bytes(token: str, path: str) -> bytes:
+    """Đọc RAW BYTES một tệp OneDrive (không ép UTF-8/không cắt) — dùng cho
+    mirror thư mục cloud xuống local, khác với :func:`read_onedrive_file` vốn
+    chỉ dành cho việc đọc nội dung văn bản vào ngữ cảnh chat."""
+    resp = _request("GET", f"/me/drive/root:/{_path_segment(path)}:/content", token)
+    return resp.content
+
+
+def upload_onedrive_file_bytes(token: str, path: str, data: bytes) -> dict:
+    """Ghi RAW BYTES vào một tệp OneDrive (tạo mới hoặc ghi đè). Xem
+    :data:`MAX_SIMPLE_UPLOAD_BYTES`."""
+    _check_upload_size(data)
+    resp = _request("PUT", f"/me/drive/root:/{_path_segment(path)}:/content", token,
+                     data=data, headers={"Content-Type": "application/octet-stream"})
+    return resp.json()
+
+
 def _encode_share_url(url: str) -> str:
     """Encode a OneDrive/SharePoint sharing URL into Graph's ``u!<base64url>``
     share-id form (see Microsoft's 'Get access to shared items' docs)."""
@@ -229,6 +263,24 @@ def list_sharepoint_files(token: str, site_id: str, path: str = "") -> List[dict
     return resp.json().get("value", [])
 
 
+def download_sharepoint_file_bytes(token: str, site_id: str, path: str) -> bytes:
+    """Đọc RAW BYTES một tệp trong thư viện tài liệu SharePoint — xem
+    :func:`download_onedrive_file_bytes`."""
+    resp = _request(
+        "GET", f"/sites/{quote(site_id)}/drive/root:/{_path_segment(path)}:/content", token)
+    return resp.content
+
+
+def upload_sharepoint_file_bytes(token: str, site_id: str, path: str, data: bytes) -> dict:
+    """Ghi RAW BYTES vào một tệp trong thư viện tài liệu SharePoint. Xem
+    :data:`MAX_SIMPLE_UPLOAD_BYTES`."""
+    _check_upload_size(data)
+    resp = _request(
+        "PUT", f"/sites/{quote(site_id)}/drive/root:/{_path_segment(path)}:/content", token,
+        data=data, headers={"Content-Type": "application/octet-stream"})
+    return resp.json()
+
+
 # ---- Teams meeting transcripts ------------------------------------------
 def find_online_meeting(token: str, join_url: str) -> List[dict]:
     """Tìm cuộc họp online theo link tham gia."""