Update multi-machine docs with reconnection implementation details,
command response propagation, and pty_created confirmation flow.
Mark reconnection as complete in phases.md, progress.md, TODO.md.
Update CLAUDE.md files with reconnection and relay response info.
Add CHANGELOG entries for new features.
Update phases.md with completed multi-machine phases A-D. Add session
entry to progress.md. Update task_plan.md decisions log and open
questions. Update multi-machine.md status to implemented. Update
CLAUDE.md files with new paths and deps. Add multi-machine section to
README.md. Mark multi-machine as done in TODO.md with new follow-up
items. Add changelog entries for all multi-machine components.
