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>

pyproject.toml

@@ -2,10 +2,11 @@
 name = "infospace-bench"
 version = "0.1.0"
 description = "Application-layer workspace for concrete structured knowledge spaces."
-requires-python = ">=3.11"
+requires-python = ">=3.12"
 dependencies = [
     "PyYAML>=6",
     "markitect-tool @ file:///home/worsch/markitect-tool",
+    "artifactstore @ file:///home/worsch/artifact-store",
 ]
 
 [project.scripts]