[@lit-labs/signals] signal set() in firstUpdated does not cause a rerender.

@sorvell is already working on this.

Since Mar 27, 2025.

### Which package(s) are affected?

@lit-labs/signals

### Description

signal set() in firstUpdated does not cause a rerender.

### Reproduction

https://stackblitz.com/edit/vitejs-vite-gqki2ufj?file=src%2Fsimple-counter.ts&terminal=dev

### Workaround

But if i wait a tick, it rerenders.
```js
protected firstUpdated(): void {
requestAnimationFrame(() => {
this.#value.set(1);
});
}
```

### Affected versions

@lit-labs/signals v0.1.2

### Browser/OS/Node environment

Browser: Chrome 134.0.6998.167