IB-WP-0014: archive integration with artifact-store (T01+T02)

Reframe IB-WP-0014 from "in-repo S3/git backend adapters" to "durable archive
surface via artifact-store". The live infospace stays in a local working folder;
finalized snapshots are bundled into content-addressed artifact-store packages.

- New module infospace_bench.archive: archive_infospace(), list_archives(),
  ArchiveRecord. Self-bootstraps a SQLite + local-FS registry under
  output/archives/.store/ when no Registry is passed in.
- New output/archives/index.yaml records each archive event (package id,
  manifest digest, retention class, included paths, file count, note).
- artifactstore added as a path dep; Python floor bumped to 3.12 to match.
- Makefile for venv-based dev setup; stack-and-commands.md updated.
- tests/test_archive.py covers index write, list, recursive-capture guard,
  caller-supplied include, and empty-include error. Full suite 65 passed.

Remaining tasks (T03 list CLI, T04 restore, T05 docs) tracked in the workplan.

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

.claude/rules/stack-and-commands.md

@@ -3,6 +3,15 @@
 The implementation stack is not established yet. Until it is, prefer
 documentation and small scaffold changes over choosing frameworks prematurely.
 
+The Python package depends on path deps (`markitect-tool`, `artifactstore`)
+that bring heavy runtime dependencies. Use the Makefile to provision a
+local venv before running tests:
+
+```bash
+make install     # creates ./.venv with all path deps
+make test        # full pytest suite (must run via .venv/bin/python)
+```
+
 Useful commands:
 
 ```bash