Fix and new features

[atomiechen]

Added

• feat(PromptConverter): add tool and array keywords for convenience
• feat(CacheManager): support only_load option
• feat(CacheManager): add ensure_dumped method
  • Example scenario: The decorated function can be called multiple times, but we only want to check files existence without loading them multiple times (which is the case of cache method).
• feat(OpenAIClient): ensure only client-wide credentials are used; API runtime credentials are ignored
• feat(OpenAIClient): support ensure_client_credentials in constructor and load obj
• feat(hprompt): support audio input (input_audio type)
• feat(hprompt): add methods for adding content parts to certain message
  • content parts: text, image, audio
• Reasoning Support:
  • feat(hprompt): now supports sub header ($$reasoning_content$$/$$content$$) for storing reasoning tokens
  • add stream_chat_with_reasoning and astream_chat_with_reasoning for streaming responses with reasoning
  • ChatPrompt: add result_reasoning to get the reasoning content string from the last message
• add option RunConfig.overwrite_if_exists: default do not overwrite already existing output paths

Fixed

• PromptConverter:
  • fix extra properties in header: should escape quotes and new lines
  • fix msgs_replace_variables(): return a deep copy when not inplace. The previous behavior returns a shallow list copy, which may cause unexpected behavior when modifying the returned object.
• ChatPrompt: ensure result_str always return a str; if content in last message is a list, return the text part if exists

Changed

• PromptConverter.msgs2raw() (ChatPrompt dump): default use tool and array keywords (instead of type="tool_calls" and type="content_array") in the dumped text. See above new feature of introducing tool and array keywords.
• ChatPrompt.add_message(): now only accepts keyword arguments
• Stream chunk type:
  • RunConfig.on_chunk(): now must receive a typed dict ChatChunkUnified with keys: role, content, reasoning_content, and tool_call
  • stream_chat_all() / astream_chat_all(): now also yield the typed dict ChatChunkUnified
• remove all DictProxy definitions and change to TypedDict, please use TypedDict for better type checking and editor support.