Which @angular/* package(s) are relevant/related to the feature request?

core

Description

Currently there is no builtin way to check that an unknown value is a writable signal or not. isSignal exists but it only tells us that the value is a Signal, not if it is writable.

Proposed solution

An isWritableSignal would be much appreciated!

Alternatives considered

Checking manually with

(isSignal(x) && 'set' in x && typeof x.set === 'function')