Add support for limiting API costs using the max_budget_usd option,
mirroring the TypeScript SDK functionality. When the budget is exceeded,
query execution stops and returns a result with subtype
'error_max_budget_usd'.
- Add max_budget_usd field to ClaudeAgentOptions
- Pass --max-budget-usd flag to Claude Code CLI
- Add test coverage for budget limit behavior
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude <noreply@anthropic.com>
