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/dashboards-json/.pi-map.md

@@ -0,0 +1,19 @@
+# monitoring/grafana/provisioning/dashboards-json
+dir: monitoring/grafana/provisioning/dashboards-json
+
+index: monitoring/grafana/provisioning/dashboards-json/.pi-map.index.md
+
+## role
+Provides declarative configuration for automatically provisioning Grafana dashboards from local JSON files.
+## files
+- dashboards.yml | Configures Grafana dashboard provisioning to automatically load and update dashboards from a JSON file directory | dep: Grafana, provisioning system, file system
+## arch
+Uses Grafana's file-based provisioning system to load dashboard definitions from a configured directory path.
+## tags
+dashboards, grafana, configures, dashboard, provisioning, automatically, load, update
+## symbols
+-
+## workflows
+-
+## dirty
+-