Update DeepSeek references from deprecated model names to the V4 lineup:
- deepseek-reasoner → deepseek-v4-pro
- deepseek-chat → deepseek-v4-flash
Keep docs and frontend mocks aligned with the wizard provider list.
This PR improves MiniMax Code Plan integration in DeerFlow by fixing three issues in the current flow: stream errors were not clearly surfaced in the UI, the frontend could not display the actual provider model ID, and MiniMax reasoning output could leak into final assistant content as inline <think>...</think>. The change adds a MiniMax-specific adapter, exposes real model IDs end-to-end, and adds a frontend fallback for historical messages.
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>