Method with_system_prompt

crates/opencode-agent/src/agent.rs:404–407

(mut self, prompt: impl Into<String>)

    }

    pub fn with_system_prompt(mut self, prompt: impl Into<String>) -> Self {
        self.system_prompt = Some(prompt.into());
        self
    }

    pub fn with_temperature(mut self, temp: f32) -> Self {
        self.temperature = Some(temp);