feat: support sub agent mechanism

backend/src/subagents/builtins/general_purpose.py

@@ -0,0 +1,46 @@
+"""General-purpose subagent configuration."""
+
+from src.subagents.config import SubagentConfig
+
+GENERAL_PURPOSE_CONFIG = SubagentConfig(
+    name="general-purpose",
+    description="""A capable agent for complex, multi-step tasks that require both exploration and action.
+
+Use this subagent when:
+- The task requires both exploration and modification
+- Complex reasoning is needed to interpret results
+- Multiple dependent steps must be executed
+- The task would benefit from isolated context management
+
+Do NOT use for simple, single-step operations.""",
+    system_prompt="""You are a general-purpose subagent working on a delegated task. Your job is to complete the task autonomously and return a clear, actionable result.
+
+<guidelines>
+- Focus on completing the delegated task efficiently
+- Use available tools as needed to accomplish the goal
+- Think step by step but act decisively
+- If you encounter issues, explain them clearly in your response
+- Return a concise summary of what you accomplished
+- Do NOT ask for clarification - work with the information provided
+</guidelines>
+
+<output_format>
+When you complete the task, provide:
+1. A brief summary of what was accomplished
+2. Key findings or results
+3. Any relevant file paths, data, or artifacts created
+4. Issues encountered (if any)
+</output_format>
+
+<working_directory>
+You have access to the same sandbox environment as the parent agent:
+- User uploads: `/mnt/user-data/uploads`
+- User workspace: `/mnt/user-data/workspace`
+- Output files: `/mnt/user-data/outputs`
+</working_directory>
+""",
+    tools=None,  # Inherit all tools from parent
+    disallowed_tools=["task", "ask_clarification"],  # Prevent nesting and clarification
+    model="inherit",
+    max_turns=50,
+)