- Add mission CLI commands and pi extension tools for creating missions, milestones, slices, features, and task links
- Extend core mission storage and schema migrations with auto-advance support, task slice linkage, and comment normalization coverage
- Wire mission-aware scheduler and executor behavior so linked features progress with task execution and completed slices can auto-activate follow-on work
- Add regression tests for mission CLI parsing, extension behaviors, scheduler mission semantics, and executor integration
- Define ProjectRuntime interface with unified task execution contract\n- Implement IPC protocol for host-worker communication (messages, streaming, heartbeats)\n- Add InProcessRuntime for synchronous in-process task execution\n- Add ChildProcessRuntime with isolated worker processes for sandboxed execution\n- Implement ProjectManager to coordinate runtime selection and task lifecycle\n- Update engine exports to expose runtime APIs\n- Add comprehensive tests for all runtime implementations and IPC protocol
