Readable from Writable
Expose only the read side of a writable store to consumers.
Why Expose Read-Only
You may want internal writes but read-only access for consumers, preventing accidental mutation.
Pattern
Keep the writable private; export an object with only the subscribe method.
const _user = writable(null);
export const user = { subscribe: _user.subscribe };
export function setUser(u) { _user.set(u); }