feat(host): add object publication and dispatch

crates/wip-interface/src/lib.rs

@@ -92,6 +92,21 @@ pub trait InterfaceDefinition {
     fn descriptor() -> InterfaceDescriptor;
 }
 
+/// Typed dispatch implemented by every generated interface companion.
+///
+/// `T` must implement the Rust interface trait associated with this definition.
+/// Host runtimes use this bound when an interface is explicitly exposed, so an
+/// object that does not implement that interface is rejected at compile time.
+pub trait InterfaceImplementation<T>: InterfaceDefinition {
+    /// Validates, decodes, and dispatches one operation to `implementation`,
+    /// then encodes and validates its result.
+    fn dispatch(
+        implementation: &T,
+        operation: &str,
+        arguments: Vec<NamedValue>,
+    ) -> Result<Option<Value>, DispatchError>;
+}
+
 /// Result convention required for generated interface operations.
 ///
 /// `Ok(T)` is an application result, including domain-failure union cases.