Server (network.py): send every record in diff mode starting from
prev={}, including the first — fixes history drop on new client connect.
Collect (collect.py): remove payload["_diff"] = True from live broadcast.
GUI client (gui_client.py): always call jay_merge_full in diff mode;
drop the _diff key check that gated reconstruction.
CLI client (client.py): fix `args.diff or True` guard that made --diff
irrelevant.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>