Function serve_router 

async fn serve_router(
    router: Arc<WorkspaceRouter>,
    mode: ServerMode,
    bind_addr: String,
    allow_remote: bool,
    tools: Arc<ToolRegistry>,
    agents: Arc<AgentRegistry>,
    extra_tools: Arc<ToolRegistry>,
    extra_agents: Arc<AgentRegistry>,
) -> Result<()>

Shared Axum wiring for both compatibility and multi-workspace modes.