Normalize OpenAI-style and LangChain standard image blocks into LangChain
standard content blocks so provider block_translators auto-convert for
either OpenAI or Anthropic. Flatten multimodal content to plain text when
persisting history and computing term embeddings.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Convert all Chinese comments, docstrings, logger/print output,
HTTPException detail messages, and API response messages to English
across the entire codebase. Functional zh/ja localized strings
(e.g. prompt templates, timezone display names, date formats) are
preserved as-is.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>