docs(kanban): describe delegated runtime attachment

Replace the north-star walkthrough's listener snippet with prose and guard example docs against teaching addEventListener glue.

req: examples/003

req: runtime/001

examples/kanban.md

@@ -285,15 +285,9 @@ Initial SSR:
 <!-- the app shell loads /slhx.js and any bootstrap state -->
 ```
 
-Runtime attachment:
-
-```js
-root.addEventListener("submit", dispatch)
-root.addEventListener("click", dispatch)
-root.addEventListener("pointerdown", dispatch)
-root.addEventListener("pointermove", dispatch)
-root.addEventListener("pointerup", dispatch)
-```
+Runtime attachment: `/slhx.js` installs delegated root listeners for forms,
+clicks, and pointer/drag events. App authors keep composing generated resources;
+they do not attach per-node listeners or write selector glue.
 
 No framework download. No VDOM. No hydration. No game loop.