Deterministic runtime-contract enrichment for packaged provider and model data.

This module upgrades descriptive catalog data into executable metadata where we have a stable contract for doing so. Providers and models we cannot execute safely are marked catalog_only: true so downstream consumers can distinguish between descriptive and executable entries without ad hoc heuristics.

Execution metadata follows one precedence rule: explicit model operation entries override provider/runtime-derived entries, which override capability and modality inference. Validation uses the same inference functions, so it cannot require an operation that enrichment would not derive.