docs(server): updated_at has decided nothing since protocol 2

The schema's comment still called it the field last-write-wins compares.
A write is decided by change_seq alone; updated_at is for display.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

server/sql/001-schema.sql

@@ -15,7 +15,9 @@ CREATE TABLE IF NOT EXISTS sync_row (
   tbl         TEXT        NOT NULL,
   pk          TEXT        NOT NULL,
   data        JSONB       NOT NULL,
-  -- The client's wall clock, and the field last-write-wins compares.
+  -- The client's wall clock, when the row was last edited. Kept for display
+  -- only: since protocol 2 (002-protocol-2.sql) nothing compares it — a
+  -- write is decided by change_seq alone.
   updated_at  BIGINT      NOT NULL,
   -- A delete. Kept as a row so it can be handed to a device that was
   -- offline when it happened.