docs(wit): document capability and component contracts

components/kv-probe/src/lib.rs

@@ -1,4 +1,12 @@
+//! Example service that exercises persistent, service-scoped Host KV.
+//!
+//! Input uses the test protocol `get:<key>`, `set:<key>:<value>`, or
+//! `delete:<key>`. Production Components should define an application-specific
+//! request format instead of copying this colon-delimited probe protocol.
+
 mod bindings {
+    // `generate_all` emits both the service export and imported KV module from
+    // the exact versions selected in `wit/world.wit`.
     wit_bindgen::generate!({
         path: "wit",
         world: "kv-probe-component",