Fix deferred subscription replay for using keyword

The `[symDispose]()` method was clearing `_subscribers` after calling
`this.f()`. With the `using _ = useSignals()` pattern, `[symDispose]`
is invoked at the end of the component function scope — before React's
commit phase where the `useIsomorphicLayoutEffect` replays the deferred
subscriptions. This wiped the captured subscribers before they could be
replayed, so signals were never actually subscribed and updates were
silently lost.

In the managed (try/finally) path, `f()` is called instead of
`[symDispose]()`, and `f()` does not clear `_subscribers` — which is
why the transform path worked correctly.

Stale subscribers from suspended renders are already handled by the
`subscribe` cleanup (clears on unmount) and the layout effect's
`_version !== -1` check (filters out dropped dependencies).

Assisted-By: devx/7d7bbf25-b015-4660-ad92-7e391d7d8929

Author: JoviDeCroock

packages/react/runtime/src/index.ts

@@ -333,7 +333,6 @@ function createEffectStore(
 		},
 		[symDispose]() {
 			this.f();
-			this._subscribers = [];
 		},
 	};