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.

monitoring/grafana/provisioning/.pi-map.md

@@ -0,0 +1,18 @@
+# monitoring/grafana/provisioning
+dir: monitoring/grafana/provisioning
+
+index: monitoring/grafana/provisioning/.pi-map.index.md
+
+## role
+Provides declarative configuration for automatic Grafana dashboard and datasource provisioning without manual UI intervention.
+## files
+## arch
+Infrastructure-as-code pattern using Grafana's native provisioning system with YAML configuration files organized into subdirectories for datasources and dashboards.
+## tags
+-
+## symbols
+-
+## workflows
+-
+## dirty
+-