Llm4sProviderModule

A unit of provider registration: everything one module contributes.

The discovered unit is a module rather than a single ProviderDescriptor so that one artifact can supply several related providers — llm4s-openai contributes OpenAI, Azure, OpenRouter and Requesty from a single entry.

Implementations must be a plain class with a public no-arg constructor, '''not''' a Scala object: java.util.ServiceLoader instantiates the named class, and an object exposes its instance as a MODULE$ field instead. Delegate to an object from the class if you want one:

class MyProviderModule extends Llm4sProviderModule:
 def chatProviders: Seq[ProviderDescriptor] = Seq(MyProvider)

Classpath discovery via META-INF/services arrives with PR 3 of #1131; until then a module is registered explicitly through ProviderRegistry.of or ProviderRegistry.withModule.