Sync watchers break subsequent updates

[skirtles-code]

Vue version

3.5.9

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

Just click the button.

What is expected?

All the watchers should log and rendering should update.

What is actually happening?

The first two watchers log, but everything after that stops reacting.

System Info

No response

Any additional comments?

I believe this is caused by 10ff159. The reproduction works correctly in 3.5.8.

The NOTIFIED flags all get cleared up front in endBatch(). The sync watcher notifies subscribers that are already in the running batch, leading to the next flag being incorrectly reset. The subscribers linked via the original next value are never run.