`@ngrx/signals`: Missing Unique Member Check for `withLinkedState`

[rainerhahnekamp]

Which @ngrx/* package(s) are the source of the bug?

signals

Minimal reproduction of the bug/regression with instructions

At the moment, this goes completely unnoticed. We should get a warning for duplicated members:

signalStore(
  withState({ value: 1 }),
  withLinkedState(() => ({
    value: () => 1,
  }))
);

Expected behavior

A warning should be shown in the console.

Versions of NgRx, Angular, Node, affected browser(s) and operating system(s)

NgRx: 20.0
Angular 20.1
Node: 22
Browser: Chrome
Operation System: MacOS

Other information

No response

I would be willing to submit a PR to fix this issue

• Yes
• No