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.

frontend/src/integrations/.pi-map.index.md

@@ -0,0 +1,23 @@
+# frontend/src/integrations (index)
+dir: frontend/src/integrations
+
+## role
+Frontend integration layer that maps backend service types and widgets to their corresponding React components, metadata, and configuration schemas.
+## parent
+index: frontend/src/.pi-map.index.md
+map: frontend/src/.pi-map.md
+## children
+-
+## files
+- registry.test.ts
+- registry.ts
+## links
+index: frontend/src/integrations/.pi-map.index.md
+map: frontend/src/integrations/.pi-map.md
+## workflows
+- change integrations behavior
+  read: registry.ts
+- update integrations tests
+  read: registry.test.ts
+## dirty
+-

frontend/src/integrations/.pi-map.md

@@ -0,0 +1,30 @@
+# frontend/src/integrations
+dir: frontend/src/integrations
+
+index: frontend/src/integrations/.pi-map.index.md
+
+## role
+Frontend integration layer that maps backend service types and widgets to their corresponding React components, metadata, and configuration schemas.
+## files
+- registry.test.ts | Tests the service and widget registry module, verifying correct service registrations, widget bindings, and widget resolution logic. | dep: vitest, ./registry, ../types
+- registry.ts | Defines a frontend registry mapping service types and built-in widgets to their React components, metadata, and config schemas, with a resolver to look up widgets by instance. | exp: WidgetComponentProps, ServiceWidgetBinding, ServiceBinding, SERVICE_REGISTRY, BUILTIN_WIDGETS, ResolvedWidget, func:getServiceBinding(serviceType: string) → ServiceBinding | undefined, func:getBuiltinBinding(kind: string) → ServiceWidgetBinding | undefined, func:resolveWidget(widget: WidgetInstance, services: ServiceInstance[]) → ResolvedWidget | undefined, call:services.find, call:getServiceBinding, call:binding?.widgets.find, call:getBuiltinBinding, func:enrichServiceTypes(types: ServiceTypeInfo[]) → ServiceTypeInfo[] | dep: react, ../widgets/AlertmanagerAlertsWidget, ../widgets/BackupsWidget, ../widgets/GrafanaLinkWidget, ../widgets/JellyfinWidget, ../widgets/PrometheusMetricWidget, ../widgets/SshTaskWidget, ../widgets/StaticWidget, ../types, AlertmanagerAlertsWidget, BackupsWidget, GrafanaLinkWidget, JellyfinWidget, PrometheusMetricWidget, SshTaskWidget, StaticWidget, types
+## arch
+Registry pattern implementing a centralized lookup dictionary with a resolver function to dynamically discover and instantiate the correct widget components based on service instances.
+## tags
+service, binding, widget, widgets, registry, types, builtin, get
+## symbols
+- getServiceBinding
+- getBuiltinBinding
+- resolveWidget
+- enrichServiceTypes
+- WidgetComponentProps
+- ServiceWidgetBinding
+- ServiceBinding
+- SERVICE_REGISTRY
+## workflows
+- change integrations behavior
+  read: registry.ts
+- update integrations tests
+  read: registry.test.ts
+## dirty
+-