Feature/delta team/epic r04 (#7)

## Summary

epic r04 - begin refactor

## Change Type

- [x] 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: Anh Tran Nguyen Minh <anhtnm1@fpt.com>
Co-authored-by: Huong Le Thi Thien <huongltt35@fpt.com>
Co-authored-by: Nam Pham Dinh Thanh <nampdt@fpt.com>
Co-authored-by: Vu Dam Tuan <vudt15@fpt.com>
Co-authored-by: Hiep Ha Van <hiephv3@fpt.com>
Co-authored-by: Lam Hoang Van <lamhv7@fpt.com>
Reviewed-on: #7
Co-authored-by: Duy Le Huu <duylh19@fpt.com>

core/link_fetch.py

@@ -48,6 +48,9 @@ _DOC_SUFFIXES = {".pdf", ".doc", ".docx", ".docm", ".xls", ".xlsx", ".xlsm",
 
 
 def _html_to_text(html: str) -> str:
+    """Rút văn bản đọc được từ HTML: bỏ script/style, đổi thẻ thành xuống dòng rồi
+    gộp khoảng trắng thừa.
+    """
     text = _SCRIPT_STYLE_RE.sub(" ", html)
     text = _TAG_RE.sub("\n", text)
     text = _WS_RE.sub(" ", text)
@@ -81,6 +84,10 @@ _ONEDRIVE_HOSTS = {"1drv.ms", "onedrive.live.com"}
 
 
 def _is_share_link(url: str) -> bool:
+    """Link này có phải link chia sẻ SharePoint/OneDrive không.
+
+    Loại link đó cần đi qua đường xác thực MS365 thay vì tải HTTP thường.
+    """
     host = (urlparse(url).hostname or "").lower()
     return bool(_SHAREPOINT_HOST_RE.search(host)) or host in _ONEDRIVE_HOSTS