docs(code-runtime): state the maxWallMs upper bound in the public Config contract

The load-time range check rejects a maxWallMs above Node's maximum
setTimeout delay, but the constraint appeared only in the README design
section. Deployments reading the Config field JSDoc, the generated config
catalog, or the README config summary saw maxWallMs described as a
positive finite wall-clock ceiling, so an out-of-range value looked valid
until plugin load failed.

packages/code-runtime/code-runtime-worker/src/index.ts

@@ -36,7 +36,9 @@ export interface Config {
   /**
    * Wall-clock ceiling in milliseconds; never pauses for anything. The
    * backstop for what busy-time cannot see (a program awaiting a promise
-   * nobody will resolve).
+   * nobody will resolve). At most `2_147_483_647` (Node's maximum
+   * `setTimeout` delay, about 24.9 days): a longer value is rejected at load
+   * because `setTimeout` would clamp it to 1 ms.
    */
   maxWallMs?: number
   /**