fix(cli): complete lifecycle acceptance contract

[mmilanez]

Summary

Completes the acceptance contract audited after PR #29:

• human-readable session open output now prints previous status, pending step, blockers, and open threads;
• hosted Node 18 lifecycle coverage now includes macOS alongside Windows and Ubuntu;
• deterministic tests cover malformed handoff state and interrupted-close registry rollback;
• the installed-tarball smoke now proves a complete two-session resume flow;
• README and CLI docs include the reproducible two-session sequence;
• package and public version surfaces advance to 2.1.1 without rewriting the preserved v2.1.0 evidence.

Validation

• npm run typecheck
• npm test — 7/7 lifecycle tests passed
• npm run test:pack — installed the exact tarball and completed two consecutive sessions, verifying the second receipt received the first terminal handoff
• template validator passed
• publish leakage sweep passed

Provenance

This is a post-July-13 Build Week completion patch. PR #29, release v2.1.0, and both preserved evidence branches remain unchanged.

Closes #28