refactor: remove agent mode and related functionality; update help and README

src/app/subagent/spawn.rs

@@ -22,23 +22,9 @@ impl AgentDefinition {
         }
     }
 
-    pub fn with_system_prompt(mut self, prompt: String) -> Self {
-        self.system_prompt = Some(prompt);
-        self
-    }
-
-    pub fn with_allowed_tools(mut self, tools: Vec<String>) -> Self {
-        self.allowed_tools = Some(tools);
-        self
-    }
-
     pub fn with_max_steps(mut self, steps: usize) -> Self {
         self.max_steps = Some(steps);
         self
     }
 
-    pub fn with_temperature(mut self, temp: f32) -> Self {
-        self.temperature = Some(temp);
-        self
-    }
 }