[P0] Add enrichment onboarding examples for trace-only to topology_api/overlay upgrades

[a-a-k]

Context

topology_api and discovery overlays are the explicit enrichment surfaces for metadata that generic traces cannot infer. The current user path from trace-only discovery to high-quality topology is still too manual.

Scope

Create onboarding material and examples that show how to close metadata gaps after a trace-only artifact is generated.

Definition of Done

• Docs include a metadata coverage checklist for teams moving from trace-only to enriched artifacts.
• Examples start with missing retry/timeout/placement/shared-resource data and close those gaps with overlays or topology_api input.
• Docs state the minimum enrichment set needed for Sheaft advanced analysis.
• Examples are validated by existing local/CI checks or a new lightweight verification script.