chore: archive observability-service-registry, track pi-map artifacts

- Archive the completed observability-service-registry SDD change into
  openspec/changes/archive/ (delivered across 5 slices; only
  jellyfin-service-registry remains active).
- Stop ignoring .pi-map.md / .pi-map.index.md so the navigation maps are
  versioned alongside the code, and add the regenerated map pairs repo-wide.

docs/superpowers/specs/.pi-map.md

@@ -0,0 +1,20 @@
+# docs/superpowers/specs
+dir: docs/superpowers/specs
+
+index: docs/superpowers/specs/.pi-map.index.md
+
+## role
+Specification documents defining approved architectural designs for major features of the media library viewer project.
+## files
+- 2026-05-08-obsidian-documentation-design.md | Defines the approved documentation structure for an Obsidian-based knowledge vault for the Manage media library viewer project, targeting developers, contributors, operators, and deployers. | dep: Obsidian, FastAPI, React, TypeScript, Vite, MUI, D3, AG Grid, Docker, Traefik, Authentik, Paramiko, PyJWT, SQLite
+- 2026-05-11-backup-monitoring-design.md | Design document for a standalone backup monitoring module with HTTP API ingestion, SQLite storage, automated alerting, and React frontend for a media library viewer application. | dep: FastAPI, React, SQLite, OIDC/JWT, D3, existing MonitoringPoller
+## arch
+Dated Markdown design documents following a specification pattern, each capturing requirements, architecture decisions, and implementation plans for distinct system components.
+## tags
+design, obsidian, 2026, 05, documentation, react, sqlite, backup
+## symbols
+-
+## workflows
+-
+## dirty
+-