chore(openspec): archive cli-core-upgrade-p6

[Drswith]

Summary

Archive completed OpenSpec change cli-core-upgrade-p6 after its implementation PR (#711) merged. Living specs already carried the accepted self-upgrade, runtime-boundaries, compatibility-contract, and product-readme deltas, including the frozen --channel contract, so this closure uses skip-specs.

The generated openspec/changes/archive/ directory is not committed, matching working-tree archive policy.

Adds a one-line keep comment under src/lifecycle/ so classify keeps run_test_matrix=true and test (macos-latest) actually runs (protect-main requires it; a pure openspec deletion would otherwise skip macOS).

Linked Artifacts

• OpenSpec: cli-core-upgrade-p6

Validation

• bun run memory:check
• bun run lint
• bun run format:check
• bun run typecheck
• bun run openspec:validate

bun run test is not applicable for behavior: the only src/ edit is a one-line keep comment with no runtime effect. Full CI matrix (including macOS) is expected after this push.

Release Intent

• Release: not applicable - OpenSpec archive closure only

Release Summary

• Not applicable - OpenSpec archive closure does not produce a release entry.

Docs Updated

• openspec/...

Scope Check

• I did not add a new ad hoc root-level Markdown file.
• I updated the relevant issue, ADR, spec, runbook, or captured the missing doc work as follow-up.
• I did not silently expand project scope without recording it explicitly.

Closure Check

• Working tree was clean before archive closure started.
• Branch was pushed and this PR is the active delivery artifact.
• OpenSpec change is already archived or queued for agent-driven archive closure.
• Release is not applicable, delegated to release automation, or verified.

Notes

• Generated by bun run openspec:archive-closure -- cli-core-upgrade-p6, then the working-tree archive folder was removed rather than committed.
• Product-path keep comment in src/lifecycle/uninstall-postcondition.ts is only to satisfy protect-main's required test (macos-latest) when the rest of the diff is OpenSpec archive cleanup.