IB-WP-0014: archive-list, restore, retention annotation, docs (T03-T05)

Round out IB-WP-0014 with the remaining archive operations and docs.

- restore_archive() and `infospace-bench restore <pkg> --target <dir>` round-trip
  a finalized package's bytes back to disk. Refuses to overwrite a non-empty
  target unless --force. --from <infospace-root> resolves the store location.
- archive-list CLI with --with-retention flag; annotate_retention() opens the
  per-infospace registry and joins each record with its current retention
  state (effective class, expires, holds, eligibility).
- docs/archive-integration.md covers when to archive, the include set,
  retention classes, storage layout, credentials policy, and the explicit
  non-goal that S3/git backends live in artifact-store.
- SCOPE.md cross-links the new doc.
- Workplan flipped to status: done. Full pytest suite: 72 passed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SCOPE.md

@@ -84,5 +84,6 @@ The repo is intentionally above the lower layers:
 - Start with: `INTENT.md`, `wiki/ProductRequirementsDocument.md`,
   `wiki/FunctionalRequirementsSpecification.md`
 - Migration assessment: `docs/markitect-main-scope-assessment.md`
+- Archive integration with `artifact-store`: `docs/archive-integration.md`
 - Workplans: `workplans/`
 - State Hub rules: `CLAUDE.md` and `.claude/rules/`