[P1] Add reference non-trace adapter example built on topology_api

[a-a-k]

Context

Bering has a strong trace and topology-file path. Product adoption will depend on how easily teams can feed topology from service catalogs, mesh exports, inventory APIs, or platform APIs without creating source-specific public contracts.

Scope

Add one reference non-trace adapter example that maps an external inventory-style input into the existing topology_api contract.

Definition of Done

• Example input and generated Bering artifact are checked in.
• Docs explain why the adapter maps back to topology_api rather than introducing a new public schema family.
• Validation covers the example artifact.
• The adapter strategy preserves the stable model/snapshot contract boundary.