- Add ProjectRuntime interface with InProcessRuntime and ChildProcessRuntime implementations
- Implement HybridExecutor for multi-project task orchestration
- Add IPC protocol for host-worker communication in child-process mode
- Implement health monitoring with automatic restart for child processes
- Add comprehensive tests for hybrid-executor and project-runtime
- Update AGENTS.md with multi-project runtime documentation
- Add changeset for hybrid-executor-runtime release
