ProviderFeatures

What a provider implementation can actually do, declared by the provider itself.

This is a '''static''' declaration made by a ProviderDescriptor, not a runtime discovery: it describes the client this build ships, so a caller can ask "will streaming work here?" without making a call and reading the error.

The flags default to true because a provider that omits them is claiming the full interface; a provider that cannot honour part of it must say so, and saying so is then visible to users rather than buried in a Left at call time. Cohere and Mistral declared streaming = false until they moved onto llm4s-openai-compatible's shared client, which streams (#925).