docs: document preventDefault() behavior for event listeners (#61184)

The `false` behavior has existed for a long time but hasn't really
been documented. It's also not _quite_ what the browser would do.

Finally, the page explicitly discourages the implicit `false` way
of preventing default. Biggest motivation (beyond code clarity) are
potential footguns like `(click)="myProp=x()"` which happens to prevent
default behavior iff `x()` happens to return `false`.

Fixes https://github.com/angular/angular.io/issues/2568

PR Close #61184

adev/src/content/guide/templates/event-listeners.md

@@ -97,3 +97,24 @@ Angular also allows you to specify [Code values for keyboard events](https://dev
 ```
 
 This can be useful for handling keyboard events consistently across different operating systems. For example, when using the Alt key on MacOS devices, the `key` property reports the key based on the character already modified by the Alt key. This means that a combination like Alt + S reports a `key` value of `'ß'`. The `code` property, however, corresponds to the physical or virtual button pressed rather than the character produced.
+
+## Preventing event default behavior
+
+If your event handler should replace the native browser behavior, you can use the event object's [`preventDefault` method](https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault):
+
+```angular-ts
+@Component({
+  template: `
+    <a href="#overlay" (click)="showOverlay($event)">
+  `,
+  ...
+})
+export class AppComponent{
+  showOverlay(event: PointerEvent): void {
+    event.preventDefault();
+    console.log('Show overlay without updating the URL!');
+  }
+}
+```
+
+If the event handler statement evaluates to `false`, Angular automatically calls `preventDefault()`, similar to [native event handler attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes#event_handler_attributes). *Always prefer explicitly calling `preventDefault`*, as this approach makes the code's intent obvious.