A client on protocol 3 does not know payload version 2. It reads a
corrected Paranoia row as the old 25 m size, and its next edit to the
page writes that row back at version 1, which every new client then
corrects a second time: the Omen end jumps 3 m.

Protocol 4 is the only one the server accepts now, for reads and
writes alike. A web tab opened before this deploy can neither see a
version 2 row nor write one; it fails its reads and keeps its unsent
edits until it reloads into the new build, which sends them as they
were made, against the old size, and they read back correctly. No
desktop build that syncs has shipped, so the live web build is the only
client this turns away.

This breaks AGENTS.md's rule that a server change keeps working with
the live web build, deliberately and for one reload. Drop this commit
to keep old tabs working at the cost of that rare double move.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>