[BUG] potential race condition in updates

[mudiageo]

Describe the bug
The current read-modify-write pattern for updates is not atomic and can cause
race conditions leading to data loss. Consider making the update operation either through a transactional adapter method or by implementing a
locking/queuing mechanism in the SyncEngine.

async function handleUpdate(table, id, partialData) {
  // 1. Read existing data from storage
  const existing = await local.adapter.findOne(table, id);

  // 2. Merge changes in application memory
  const merged = { ...existing, ...partialData };

  // Another update could happen here, making `existing` stale.

  // 3. Write the merged data back to storage
  await local.adapter.update(table, id, merged);
}

Possible Solution(s):

async function handleUpdate(table, id, partialData) {
  // Delegate the update to an atomic operation in the adapter.
  // The adapter is responsible for ensuring the read-modify-write
  // cycle is atomic, preventing race conditions.
  await local.adapter.atomicPartialUpdate(table, id, partialData);
}

// Example implementation in the adapter layer:
class LocalAdapter {
  atomicPartialUpdate(table, id, partialData) {
    // This logic should be executed within a transaction
    // provided by the underlying database (e.g., IndexedDB).
    const record = this.findOne(table, id);
    const merged = { ...record, ...partialData };
    this.update(table, id, merged);
  }
}

Environment:

• sveltekit-sync version: affects all current versions
• SvelteKit version:
• Node version:
• Browser (if applicable):

Additional context
Any other relevant information.