Returns pre-computed metrics for a specific OOH asset/frame, optimized for
low-latency programmatic decisioning.

Use cases:

• Bid-time augmentation in programmatic OOH transactions
• Real-time impression valuation
• Supply-side analytics

Request options:

• inventory: Provide known asset_id/frame_id for exact lookup
• context: Provide unit characteristics for estimation when asset is not in inventory

At least one of inventory or context must be provided.

Response: Returns metrics for the specified exposure layer and optional
audience definition. Default layer is audience.