Switching pages made the target page active and dropped the current
page's server copy before reading the target. When that read failed
(offline, say), the switch reverted, but the page on screen no longer
had a server copy to compare edits against, so every later edit stayed
on the canvas and never reached the durable queue. A crash or forced
close lost them; a real release build against a stopped local Convex
showed exactly that.

The switch now reads the target page first and changes nothing unless
the read works. A failed read leaves the page on screen as it was,
still queueing its edits, and says the page couldn't be opened. With
the connection known down it fails at once instead of waiting out the
read's 30 s timeout.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>