Support auto save annotation

[eromoe]

I got The original annotation output file (b7xne11zr.output) no longer exists ( continue from error) in claude .

claude analysis :

The annotation session was interrupted before commit (the status was killed), so the annotation data was not persisted.

Plannotator works by temporarily storing the annotation data in the browser memory, and only when you click Submit (Submit) will it be sent to the server via /api/feedback and saved. The annotation is missing because the previous service process was terminated.

---

This is very frustrate as I wrote massive comments and it lost all.

[backnotprop]

We're live in 0.11.0