docs(wit): document capability and component contracts

components/counter/src/lib.rs

@@ -1,6 +1,14 @@
+//! Minimal stateful Component used to demonstrate a warm Actor Store.
+//!
+//! Invoke returns an eight-byte little-endian counter. The value survives
+//! calls to the same Actor but resets on `init`, restart, or process recovery.
+
 use core::sync::atomic::{AtomicU64, Ordering};
 
 mod bindings {
+    // Bindings are generated from `wit/world.wit` plus materialized
+    // `wit/deps`; WIT is a compile-time ABI contract, not downloaded at run
+    // time and not executed as code.
     wit_bindgen::generate!({
         path: "wit",
         world: "counter-component",