feat: add MiniMax as LLM evaluation provider

[octo-patch]

Summary

Add MiniMax as an alternative LLM provider for GPT-based model evaluation, alongside OpenAI and Azure OpenAI.

MiniMax provides OpenAI-compatible chat completion models (M2.7, M2.5, M2.5-highspeed) that can serve as AI judges for evaluating fine-tuned model outputs.

Changes

• Metrics (text_causal_language_modeling_metrics.py): Extend get_openai_client() factory to support MiniMax via OPENAI_API_TYPE=minimax or auto-detection when MINIMAX_API_KEY is set and OPENAI_API_KEY is not
• Config (text_causal_language_modeling_config.py): Add MiniMax-M2.7, MiniMax-M2.5, MiniMax-M2.5-highspeed to the predefined metric model dropdown
• Validation (utils.py): Update check_metric() to preserve GPT metric when MINIMAX_API_KEY is available
• Settings UI (settings.py): Add MiniMax API Token field in the settings page
• Environment (app_utils/utils.py, config.py): Wire MINIMAX_API_KEY through training environment variables and default settings
• Documentation: Update evaluation guide with MiniMax setup instructions and tooltip descriptions

Usage

Option 1 — Auto-detect (simplest):

export MINIMAX_API_KEY="your-key"
# No OPENAI_API_KEY needed — MiniMax is used automatically

Option 2 — Explicit selection (when both keys are set):

export OPENAI_API_TYPE=minimax
export MINIMAX_API_KEY="your-key"

Then select MiniMax-M2.7 (or M2.5 / M2.5-highspeed) as the Metric Gpt Model in the experiment configuration.

Test plan

• 7 unit tests for get_openai_client() covering all provider paths (default OpenAI, MiniMax via API type, MiniMax auto-detect, preference when both keys set, explicit override, custom base URL, Azure)
• 2 new unit tests for check_metric() with MiniMax key scenarios
• 3 integration tests for MiniMax provider (auto-detect client, explicit client, check_metric preservation)
• 1 live integration test calling MiniMax API (skipped when MINIMAX_API_KEY not set)
• All 7 existing BLEU score tests continue to pass
• All 2 existing check_metric tests continue to pass

11 files changed, 259 additions(+), 14 deletions(-)