I am not sure why you have a separate folder for signals, but since it mentions Angular17, the signal function has a second argument (CreateSignalOptions), which is an object with property equals, this defines when the signal event is considered a change.

Usually, for primitive types (as in your case number) the actual value has to change for the signal to trigger a change, but you have this property equals, which can be used to manipulate this logic, to fire even when there is no actual change.

...
export class App {
  count = signal<number>(0, {
    equal: (a: number, b: number) => false,
  });
  ...

Full Code:

import { Component, signal, computed, effect } from '@angular/core';
import { bootstrapApplication } from '@angular/platform-browser';
import { TestArraysCmp } from './testing-arrays.component';
import { TestObjectsCmp } from './testing-objects.component';
import 'zone.js';

@Component({
  selector: 'app-root',
  standalone: true,
  template: `
    <div>Count: {{ count() }}</div>
    <div>Double: {{ double() }}</div>

    <button (click)="inc()">Increase</button>
    <button (click)="reset()">Reset</button>

    <br>
    <!-- <test-arrays /> -->
    <!-- <test-objects /> -->

  `,
  imports: [TestArraysCmp, TestObjectsCmp],
})
export class App {
  count = signal<number>(0, {
    equal: (a: number, b: number) => false,
  });

  double = computed(() => this.count() * 2);

  countType = computed(() => (this.count() % 2 === 0 ? 'even' : 'odd'));

  constructor() {
    effect(() => {
      console.log('Count changed', this.count());
      console.log(this.count(), 'is', this.countType());
    });
  }

  inc() {
    this.count.update((c) => c + 0);
  }

  reset() {
    this.count.set(0);
  }
}

bootstrapApplication(App);

Stackblitz Demo

In many reactive systems, signals are designed not to emit events when the value remains unchanged to avoid redundant updates. This seems to be the case in your example, where updating the count by 0 does not trigger any event because the value does not change.
But as @Naren said there is a way to ignore it by using CreateSignalOptions.