sync: add aichat resource (POST /aichat/conversations)

[Copilot]

The aichat service was absent from both SDKs despite being defined in the Docs OpenAPI spec. This adds it as a first-class resource alongside the existing chat and openai namespaces.

Changes

• New AiChat resource (TypeScript + Python, sync + async) — wraps POST /aichat/conversations with typed params: required model + question, optional id, preset, stateful, references
• AiChatModel type — union/Literal covering all 78 models from the spec (GPT-5.x, GPT-4.x, o1/o3/o4-mini, DeepSeek, Grok-3, GLM series)
• Client wiring — client.aichat exposed on both AceDataCloud and AsyncAceDataCloud
• Public exports — AiChatModel added to index.ts and __init__.py

Usage

const reply = await client.aichat.create({
  model: 'gpt-4o',
  question: 'What is the capital of France?',
});
console.log(reply.answer);

reply = client.aichat.create(model="gpt-4o", question="What is the capital of France?")
print(reply["answer"])