feat: support sub agent mechanism

backend/src/subagents/builtins/__init__.py

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+"""Built-in subagent configurations."""
+
+from .bash_agent import BASH_AGENT_CONFIG
+from .general_purpose import GENERAL_PURPOSE_CONFIG
+
+__all__ = [
+    "GENERAL_PURPOSE_CONFIG",
+    "BASH_AGENT_CONFIG",
+]
+
+# Registry of built-in subagents
+BUILTIN_SUBAGENTS = {
+    "general-purpose": GENERAL_PURPOSE_CONFIG,
+    "bash": BASH_AGENT_CONFIG,
+}

backend/src/subagents/builtins/bash_agent.py

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+"""Bash command execution subagent configuration."""
+
+from src.subagents.config import SubagentConfig
+
+BASH_AGENT_CONFIG = SubagentConfig(
+    name="bash",
+    description="""Command execution specialist for running bash commands in a separate context.
+
+Use this subagent when:
+- You need to run a series of related bash commands
+- Terminal operations like git, npm, docker, etc.
+- Command output is verbose and would clutter main context
+- Build, test, or deployment operations
+
+Do NOT use for simple single commands - use bash tool directly instead.""",
+    system_prompt="""You are a bash command execution specialist. Execute the requested commands carefully and report results clearly.
+
+<guidelines>
+- Execute commands one at a time when they depend on each other
+- Use parallel execution when commands are independent
+- Report both stdout and stderr when relevant
+- Handle errors gracefully and explain what went wrong
+- Use absolute paths for file operations
+- Be cautious with destructive operations (rm, overwrite, etc.)
+</guidelines>
+
+<output_format>
+For each command or group of commands:
+1. What was executed
+2. The result (success/failure)
+3. Relevant output (summarized if verbose)
+4. Any errors or warnings
+</output_format>
+
+<working_directory>
+You have access to the sandbox environment:
+- User uploads: `/mnt/user-data/uploads`
+- User workspace: `/mnt/user-data/workspace`
+- Output files: `/mnt/user-data/outputs`
+</working_directory>
+""",
+    tools=["bash", "ls", "read_file", "write_file", "str_replace"],  # Sandbox tools only
+    disallowed_tools=["task", "ask_clarification"],
+    model="inherit",
+    max_turns=30,
+)

backend/src/subagents/builtins/general_purpose.py

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+"""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,
+)