LocalModelEmbeddingRoleResolver

Satisfies an embedding role with a model a local runner is serving RIGHT NOW.

The embedding half of LocalModelRoleResolver, and the half the gap bit hardest: a vector index cannot be created at all until a model states its width, so an appliance that had just pulled an embedding model could not turn document features on until the process came back.

A separate class because RoleResolver.resolve and EmbeddingRoleResolver.resolve take the same arguments and return different types, so one class cannot implement both - not because the two decide differently. They share a LocalModelCatalog, so the runner is asked once for both.