docs(wit): document capability and component contracts

components/echo/src/lib.rs

@@ -1,4 +1,8 @@
+//! Smallest request/response Component example: it returns input bytes unchanged.
+
 mod bindings {
+    // Generate the guest trait and export adapter from the selected WIT world.
+    // Dependency sync must populate `wit/deps` before this macro is compiled.
     wit_bindgen::generate!({
         path: "wit",
         world: "echo-component",

components/echo/wit.lock

@@ -4,5 +4,5 @@ schema_version = 1
 name = "wasmeld:service"
 version = "0.1.0"
 source = "path+../../wit/service"
-sha256 = "d5497307bbcd1e159f7707f385b488a6f2e26362d5256d5bc1080ac603a51305"
+sha256 = "1b2069606ccbf5202789667570bc824f702f34b147aa38e81c2ab677444ffa0e"
 replaced = true

components/echo/wit/world.wit

@@ -1,5 +1,6 @@
 package component:echo@0.1.0;
 
+/// Echo only needs the base service lifecycle and imports no Host capability.
 world echo-component {
   include wasmeld:service/service-component@0.1.0;
 }