Emit usage updates from Claude stream events#506

Mng-dev-ai wants to merge 2 commits intoagentclientprotocol:mainagentclientprotocol/claude-agent-acp:mainfrom

Mng-dev-ai:fix/stream-event-usage-updatesMng-dev-ai/claude-agent-acp:fix/stream-event-usage-updatesCopy head branch name to clipboard