Stepper step-panels not lazily rendered

Describe the bug

We recently migrated from PrimeNG v17 to PrimeNG v21.

It seems like in v21, the contents of all the p-step-panels are rendered on the stepper initialisation, while they were lazily rendered at each step activation before.

There is closed bug for v20 that was fixed, #18561, but it seems like it is still eagerly rendered in v21, which breaks our application, because there are states updates and ngInit tasks in the components of each step-panel, that depend on each other, but are now executed on the first stepper step.

I could be wrong but it could be a side effect of the eagerly rendering of the Tabs panels, which could have been applied to the Stepper as well. But the Tabs has a global [lazy]="true" flag which can be used to render each panel lazily, which the Stepper is lacking at the moment.

Expected behaviour: Add lazy input prop to Stepper.

Pull Request Link

No response

Reason for not contributing a PR

• Lack of time
• Unsure how to implement the fix/feature
• Difficulty understanding the codebase
• Other

Other Reason

No response

Reproducer

https://stackblitz.com/edit/github-pjvaqhva

Environment

Angular 21, zoneless PrimeNG 21

Angular version

21.2.4

PrimeNG version

v21

Node version

22.13

Browser(s)

Edge

Steps to reproduce the behavior

• create a Stepper with at least 2 steps,
• in each of the step-panels' template add a child component, that has a ngOnInit with console log inside.
• check the console in devTools

Expected behavior

There must be lazy input like for Tabs, to lazily render the step panels