fix: a change made while an earlier save is running is stored (closes #448)

saveStateOnce() took its baseline from the page's state after the write, so
a change made while the save waited on storage counted as already stored and
the save queued after it wrote nothing. A setting changed during the read was
lost, and so was a wallet added, a site revoked or an endpoint changed during
the write. The save now copies the page's fields when it starts, writes from
that copy, and keeps the copy as the baseline, so anything changed after the
copy is still a difference for the next save.

Model: opus-5-5

TODO.md

@@ -45,6 +45,16 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-05: A change made while an earlier save from the same page is still
+  running is stored ([#448](https://git.eeqj.de/sneak/AutistMask/issues/448)).
+  `saveStateOnce()` took its baseline from the page's state after the write, so
+  a change made while the save waited on storage counted as already stored and
+  the save queued after it wrote nothing. A setting changed during the read was
+  lost; so was a wallet added, a site revoked or an endpoint changed during the
+  write, and a wallet deleted then stayed in storage. The save now copies the
+  page's fields when it starts, writes from that copy, and keeps the copy as the
+  baseline.
+
 - 2026-10-05: The extension no longer opens a window for a site-connection
   prompt already answered
   ([#287](https://git.eeqj.de/sneak/AutistMask/issues/287)). When the prompt was