soma serve routes only the cell that owns request

Pitfall 10 of writing Soma, the programming language: a habit from another language, or a rule that surprises, with what the Soma compiler answers and the form to write.

// other cells' signals are NOT auto-routed as HTTP endpoints

// put every routable signal on the request-owning cell, delegating
// to domain cells:
cell Api {
    face { signal request(...) -> String  signal place(...) -> Map }
    on place(...) { return place_order(...) }   // delegate to Orders
    on request(method: String, path: String, body: String) { ... }
}