fix(agent): treat tool_use/tool_result as atomic groups in history pruning#4825

SimianAstronaut7 merged 2 commits intozeroclaw-labs:masterzeroclaw-labs/zeroclaw:masterfrom

singlerider:fix/pruner-tool-group-atomicsinglerider/zeroclaw:fix/pruner-tool-group-atomicCopy head branch name to clipboard