feat: add present_file tool

backend/src/tools/builtins/present_file_tool.py

@@ -0,0 +1,24 @@
+from langchain.tools import tool
+
+
+@tool("present_files", parse_docstring=True)
+def present_file_tool(filepaths: list[str]) -> str:
+    """Make files visible to the user for viewing and rendering in the client interface.
+
+    When to use the present_files tool:
+
+    - Making any file available for the user to view, download, or interact with
+    - Presenting multiple related files at once
+    - After creating a file that should be presented to the user
+
+    When NOT to use the present_files tool:
+    - When you only need to read file contents for your own processing
+    - For temporary or intermediate files not meant for user viewing
+
+    Args:
+        filepaths: List of absolute file paths to present to the user. **Only** files in `/mnt/user-data/outputs` can be presented.
+
+    Returns:
+        "OK" if the files were presented successfully.
+    """
+    return "OK"