feat: support sub agent mechanism

backend/src/subagents/builtins/bash_agent.py

@@ -0,0 +1,46 @@
+"""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,
+)