0.4.0

• feat: add the ModelKit API (sdk.modelkit) with task-oriented model listing and OpenAI-compatible chat / embedding / asr / tts clients under /modelkit/*; document it in README/README-zh_CN and use it in the example.
• feat: add AgentOSSDK(connectTimeout:, receiveTimeout:) options for long-running stream configuration.
• feat: add managed AppKit subscription lifecycle with agentos.subscribe(...) and AgentOSSDK.dispose().
• feat: keep agentos.subscribe(AgentOSEventHandler) signature unchanged while making it idempotent during active subscriptions.
• docs: clarify unified AgentOSSDK public import usage, subscription lifecycle, and long-running timeout configuration.