chore(openspec): drop working-tree archive history

[Drswith]

Summary

Remove leftover openspec/changes/archive/ from the working tree so completed OpenSpec archaeology lives only in git history, matching project-memory.

Scope correction: this PR does not archive the deferred in-flight changes. These remain in openspec/changes/ and are left alone:

• release-one-line-delivery
• release-pr-skip-human-heuristics
• windows-ci-advisory-merge-gate
• restore-managed-update-and-resume-releases (still incomplete)

fix-upgrade-unresolved-latest-crash was already archived via #707 and is not touched here.

Also adds a one-line product-path keep comment under src/lifecycle/ so classify sets run_test_matrix=true and test (macos-latest) runs (protect-main requires it).

Linked Artifacts

• OpenSpec: not required - working-tree archive cleanup plus a no-op product-path keep comment; no new behavior contracts
• Related: chore(openspec): archive fix-upgrade-unresolved-latest-crash #707 (already merged archive of fix-upgrade-unresolved-latest-crash)

Validation

• bun run memory:check
• bun run lint
• bun run format:check
• bun run typecheck
• bun run test (if behavior changed)
• Not run, explained below

bun run openspec:validate passed. 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 - docs/process/test-only change

Release Summary

• Not applicable - this source PR does not produce a release entry.

Docs Updated

• openspec/changes/archive/** removed (history retained in git)
• docs/...

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 after commit.
• Branch was pushed and this PR is the active delivery artifact.
• OpenSpec change is not needed, still active until this merge, active across milestone merges by design, queued for agent-driven archive closure after completion, or already archived.
• Release is not applicable, delegated to release automation, or verified.

Notes

• Rebased/reset onto latest main after chore(openspec): archive fix-upgrade-unresolved-latest-crash #707 merged.
• No YAML, SDK, CLI contract, protect-main, or fixtures-acceptance edits.
• Companion docs wording PR: docs: refresh post-1.12 runbook/ADR wording #709.