feat: implement subagent tool gating and timeout mechanisms for enhanced security and performance

src/app/subagent/spawn.rs

@@ -35,4 +35,15 @@ impl AgentDefinition {
         self
     }
 
+    /// Builder method: set the system prompt for this agent.
+    pub fn with_system_prompt(mut self, prompt: String) -> Self {
+        self.system_prompt = Some(prompt);
+        self
+    }
+
+    /// Builder method: set the allowed tool list for this agent.
+    pub fn with_allowed_tools(mut self, tools: Vec<String>) -> Self {
+        self.allowed_tools = Some(tools);
+        self
+    }
 }