[PowerSync]: Replacing optimistic state after insert

• [ X] I've validated the bug against the latest version of DB packages

Describe the bug
When using powersync-db-collection, I wish to create a model with a temporary id, awaiting that mutation, then return the server-confirmed model result from my create method - entailing "swapping" the optimistic model for the confirmed model.

However, this is not possible for two reasons:

• await tx.isPersisted.promise resolves when the mutation resolves, not when the data has been synced via Powersync.
• Similar to the problem described in https://github.com/TanStack/db/issues/893 - once the data is synced, there is no mechanism to replace optimistic data. So the temporary model remains alongside the confirmed.

Current Behavior

const tx = todosCollection.insert({
  id: tempId,
  name,
})

await tx.isPersisted.promise
// Problem: Resolved without confirmed data yet in client
// If there were, we could use view-key mapping to swap out optimistic data for real, described here: https://tanstack.com/db/latest/docs/guides/mutations#solution-3-maintain-a-view-key-mapping

Expected behavior
There should be a way to await syncing of the confirmed data, and to swap out optimistic data for confirmed.

No file or test is named. Start with the powersync-db-collection insert flow and the tx.isPersisted.promise behavior described in the report, then trace when confirmed data reaches the client. Done should cover awaiting synced data and replacing the temporary model without leaving a duplicate.