Schema export: publish chat history input types

[ncoghlan]

In addition to the chat history message format used to communicate with the LM Studio server, lmstudio-js also defines chat message formats that are more convenient for appending messages when using the SDK:

• Simple text system prompt: {role: "system", content: "A text string"}
• Simple text user messages: {role: "user", content: "A text string"}
• User messages with attached image file handles: {role: "user", content: "A text string", images: [image_handle]}
• Simple text assistant responses: {role: "assistant", content: "A text string"}

While some input-only types (such as the prediction config interfaces) are currently published as part of the schema export, these chat history input formats are not currently exported.

Exporting these types will reduce the potential for divergence between the dict formats accepted by lmstudio-python and those accepted by lmstudio-js.

[ncoghlan]

For clarification, image_handle above refers to the ChatMessagePartFileData wire format, rather than to an internal file handle.