Remapped all issue references in ARC42STORIES.MD §9 from the previous tracker to the current casehubio/casehub-pages GitHub issues.

The ARC42STORIES.MD was generated from a LAYER-LOG.md that tracked work under a different issue numbering scheme. Every #N reference in §9 — chapters, backlog, and the §12 risk table — pointed to a tracker that no longer exists.

What changed:

• Chapters 1 and 2 converted from stale issue tables to milestone tables. Both chapters are complete — the issue numbers were noise, the milestone descriptions are the value.
• Backlog replaced entirely with the 14 current open issues (#12–#26) from casehubio/casehub-pages.
• §12 risk reference updated from old #3 (JSONata bridge) to current #16 (CSP compliance).

One commit, one file, 43 insertions / 40 deletions. Mechanical but necessary — every #N link in the document now resolves to a real GitHub issue.