feat(platform): verify local OTel metadata metrics

[zhouning]

Stacked on #9.

Summary

• add a digest-pinned, ephemeral OTel Collector and upstream JSON Exporter pipeline for OpenMetadata and Gravitino
• verify two scrape intervals through an allowlisted evidence projection, then remove all temporary Kubernetes resources
• register the local-only runtime, CI contract, ADR-042, roadmap state, and committed live evidence

Live evidence

• both jobs remained up=1 across two observations separated by 6.033 seconds
• OpenMetadata scraped 417 samples and Gravitino scraped 5 samples in each observation
• all 11 temporary resources and the loopback port-forward were removed; provider identities were preserved
• evidence fingerprint: 32842b77d23f23b1cb298ec649771c46bc4ce4004ea1efd311f30d5847c7dc82

Verification

• 510 required platform tests passed
• 21 focused OTel/platform-truth tests passed
• metadata OTel evidence integrity verified
• Kubernetes kustomize render and CI YAML validation passed
• frontend production build passed

Claim boundary

This proves only local_otel_metrics_pipeline_verified and local_repeated_scrape_verified. Generic/production OTel, persistent storage, TLS, tenant isolation, alert delivery, SLOs, NetworkPolicy enforcement, and production readiness remain false.