Agent builder: expanded Version History

The Agent Builder now includes an expanded Version History panel. You can browse past versions of an agent and, for each one, see a line-by-line comparison of what changed in the agent's instructions — so it's clear exactly what was different between versions.

Previously, Version History only tracked an agent's instructions and model, and those were the only things you could restore from a past version. Now it covers every aspect of an agent — identity, instructions, model, tools, knowledge files, custom actions, and triggers — and you can optionally restore any of these when reverting to an earlier version. Restoring is no longer all-or-nothing: bring back just the parts you want, on their own, without reverting everything else. And if a teammate publishes changes to the same agent while you're editing, you'll be warned rather than silently overwriting their work, with the option to review or merge their updates into yours.