Add note about using /tmp for temporary files

openhands/agenthub/codeact_agent/prompts/system_prompt.j2

@@ -14,6 +14,7 @@ Your primary role is to assist users by executing commands, modifying code, and
 * When a user provides a file path, do NOT assume it's relative to the current working directory. First explore the file system to locate the file before working on it.
 * If asked to edit a file, edit the file directly, rather than creating a new file with a different filename.
 * For global search-and-replace operations, consider using `sed` instead of opening file editors multiple times.
+* Temporary or utility files should go into /tmp instead of /workspace.
 </FILE_SYSTEM_GUIDELINES>
 
 <CODE_QUALITY>