Fix: guard resetPersistence when not initialized in syncState.reset

[claushaas]

Context
When syncStateValue.reset() is called early (before loadLocal initializes persistence), resetPersistence is still undefined. reset() calls syncStateValue.resetPersistence() unconditionally, which throws:
TypeError: syncStateValue.resetPersistence is not a function (it is undefined).

Steps to reproduce

Call syncState(obs).reset() immediately after creating a synced observable.
In async persistence setups, reset can run before loadLocal finishes.
Root cause
resetPersistence is only assigned inside loadLocal(...). Until then it’s undefined, but reset() calls it without a guard.

Change
Replace the direct call with a safe optional call and fallback.

How this fixes it
Prevents the exception and allows reset() to work even when called before persistence initialization, without changing behavior once resetPersistence exists.

Patch

• const promise = syncStateValue.resetPersistence();

• const promise = syncStateValue.resetPersistence?.() ?? Promise.resolve();
  Notes
  This is backward-compatible and no-op when persistence has already been initialized.

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[Copilot]

Pull request overview

This PR fixes a runtime TypeError that occurs when reset() is called on a synced observable before its persistence layer has been initialized. The issue arises because resetPersistence is only assigned during the asynchronous loadLocal function, but the type system assumes it's always defined.

Changes:

• Added optional chaining and nullish coalescing to safely call resetPersistence?.() in the reset() function
• Falls back to Promise.resolve() when resetPersistence is undefined

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