feat: allow custom event names in ComfyApi.addEventListener (#9140)

## Summary
- Add string fallback overloads to `addEventListener` and
`removeEventListener` on `ComfyApi`
- Extensions can now listen for custom event names without TypeScript
rejecting unknown event names
- Known events still get full type safety via the generic overload;
unknown strings fall through to `CustomEvent`

## Related Issue
- Fixes #2088

## QA
- Verify existing typed event listeners (e.g.
`api.addEventListener('status', ...)`) still infer correct types
- Verify custom event names (e.g.
`api.addEventListener('my-custom-event', ...)`) compile without errors

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9140-feat-allow-custom-event-names-in-ComfyApi-addEventListener-3116d73d36508128aad3fab98c34fac3)
by [Unito](https://www.unito.io)

src/scripts/api.ts

@@ -475,6 +475,23 @@ export class ComfyApi extends EventTarget {
     super.removeEventListener(type, callback as EventListener, options)
   }
 
+  addCustomEventListener(
+    type: string,
+    callback: ((event: CustomEvent<unknown>) => void) | null,
+    options?: AddEventListenerOptions | boolean
+  ) {
+    super.addEventListener(type, callback as EventListener, options)
+    this._registered.add(type)
+  }
+
+  removeCustomEventListener(
+    type: string,
+    callback: ((event: CustomEvent<unknown>) => void) | null,
+    options?: EventListenerOptions | boolean
+  ) {
+    super.removeEventListener(type, callback as EventListener, options)
+  }
+
   /**
    * Dispatches a custom event.
    * Provides type safety for the contravariance issue with EventTarget (last checked TS 5.6).