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>

application/workspaces/file_workspace_service.py

@@ -0,0 +1,84 @@
+"""FileWorkspaceService - the safe file operations File Explorer and the AI
+File Editor need, outside the agent tool loop (R06-T05).
+
+``ui/folder_tab.py`` (File Explorer) and the AI File Editor dialog need the
+exact same guarantees the agent's tools already have — path containment
+inside the workspace, precise context-anchored edits, syntax warnings on a
+bad Python write — but today that logic only exists wired to a model's tool
+call (``core/tools.py::execute_tool``). A UI action that isn't a tool call
+(browsing the tree, applying an AI-suggested diff from a review dialog) has
+no equivalent entry point of its own.
+
+This service IS that entry point. It reuses ``core/tools.py::execute_tool``
+verbatim - same dispatch table, same ``ToolContext`` containment check, same
+audit-log entry, same Python-syntax warning on write/edit - rather than
+re-implementing any of it, so a fix to one path fixes both. It only adds the
+:class:`~domain.workspaces.workspace_session.WorkspaceSession` seam: which
+workspace root a call is scoped to is decided by the session, not by
+whichever folder a widget happens to have open.
+"""
+from __future__ import annotations
+
+from typing import Any, Dict
+
+
+class FileWorkspaceService:
+    """File operations scoped to one :class:`WorkspaceSession`.
+
+    Read-only by name (``list_tree``/``read_preview``) vs. writing
+    (``write_file``/``apply_edit``) mirrors the same READ/WRITE split
+    ``domain/tools/tool_registry.py`` uses for the agent's own tools - a
+    caller that only wants to browse never accidentally has write access.
+    """
+
+    def __init__(self, session) -> None:  # WorkspaceSession - see module docstring
+        """Nhận một ``WorkspaceSession`` — mọi đường dẫn về sau đều bị nó chặn trong
+        phạm vi cho phép.
+        """
+        self._session = session
+
+    def list_tree(self, rel: str = ".") -> Dict[str, Any]:
+        """Entries at ``rel`` (default: the workspace root)."""
+        return self._execute("list_dir", {"path": rel})
+
+    def read_preview(self, rel: str) -> Dict[str, Any]:
+        """A text file's content (truncated by
+        ``infrastructure/filesystem/file_tools.py::MAX_READ_BYTES``, same as
+        the agent's ``read_file`` tool)."""
+        return self._execute("read_file", {"path": rel})
+
+    def write_file(self, rel: str, content: str) -> Dict[str, Any]:
+        """Create or fully overwrite ``rel``."""
+        return self._execute("write_file", {"path": rel, "content": content})
+
+    def apply_edit(self, rel: str, old_string: str, new_string: str,
+                   replace_all: bool = False) -> Dict[str, Any]:
+        """Replace an exact snippet in an existing file - the same
+        context-anchored algorithm the agent's ``edit_file`` tool uses, so an
+        AI-suggested diff applies with the same precision and the same
+        "old_string not found / ambiguous" failure messages either path
+        would give the caller."""
+        return self._execute("edit_file", {
+            "path": rel, "old_string": old_string, "new_string": new_string,
+            "replace_all": replace_all,
+        })
+
+    # -- internals --------------------------------------------------------- #
+    def _tool_context(self):
+        """A ``ToolContext`` scoped to this session's workspace root.
+        ``flatten_writes=False`` (unlike Cowork's agent context) - File
+        Explorer must preserve whatever subfolder structure the user is
+        actually browsing, not collapse every write into the root."""
+        from cowork_local.infrastructure.filesystem.tool_context import ToolContext
+
+        return ToolContext(self._session.workspace_root, flatten_writes=False)
+
+    def _execute(self, name: str, args: Dict[str, Any]) -> Dict[str, Any]:
+        """Dispatch through ``core/tools.py::execute_tool`` - see the module
+        docstring for why this delegates instead of reimplementing."""
+        from cowork_local.core.tools import execute_tool
+
+        return execute_tool(self._tool_context(), name, args)
+
+
+__all__ = ["FileWorkspaceService"]