stable-v1.0.5 — gke-prom overlay + Path B Spectral re-enable

Stability checkpoint covering:

obs:
- ServiceMonitor for Mirador app in local-prom overlay (#108)
- gke-prom/ overlay: kube-prometheus-stack on GKE Autopilot (#109)
  · 7-day retention, 10Gi PVC on standard-rwo, 1.5Gi mem cap
  · 6 ServiceMonitors (kubelet, apiserver, coreDNS + 3 chart svcs)
  · Coexists with lgtm OTel-native pod (Option B, ADR-0039)
- ADR-0039 GKE deployment section + TASKS follow-ups

openapi:
- OpenApiCustomizer bean (OpenApiConfig#openApiSchemaSanitizer) (#110)
  · Strips springdoc MissingNode/NullNode default tokens
  · Drops empty-string defaults on non-string types and string-format types
  · Normalises parameter examples to schema type (coerce or drop)
- 13 unit tests in OpenApiSchemaSanitizerTest
- .spectral.yaml: re-enables oas3-valid-schema-example +
  oas3-valid-media-example at error severity (24 errors → 0)
- ADR-0037 marked superseded with Path B addendum