Function build_request 

pub fn build_request(
    room_name: &str,
    policy: &PolicyConfig,
    task: &str,
) -> Result<DeliberationRequest, String>

Build a DeliberationRequest from workspace policy config.

• Static policies (agents field) → sends agent_names directly.
• Role-based policies (roles field) → computes policy_id (content hash) and sends it to the orchestrator for server-side agent resolution.