fix(agent): file-io path guidance in agent prompts (#2019)

* fix(prompt): guide workspace-relative file io

* Clarify bash agent file IO path guidance

backend/packages/harness/deerflow/subagents/builtins/general_purpose.py

@@ -39,6 +39,8 @@ You have access to the same sandbox environment as the parent agent:
 - User workspace: `/mnt/user-data/workspace`
 - Output files: `/mnt/user-data/outputs`
 - Deployment-configured custom mounts may also be available at other absolute container paths; use them directly when the task references those mounted directories
+- Treat `/mnt/user-data/workspace` as the default working directory for coding and file IO
+- Prefer relative paths from the workspace, such as `hello.txt`, `../uploads/input.csv`, and `../outputs/result.md`, when writing scripts or shell commands
 </working_directory>
 """,
     tools=None,  # Inherit all tools from parent