feat: add MiniMax models to Model Config

[octo-patch]

Reason: Add the target provider and models to the existing provider registry.

Summary

• Register MiniMax M3 and MiniMax M2.7 in the model selector data.
• Document global and China endpoint setup for both supported API protocols.
• Add registry and request-path coverage for all supported endpoint combinations.

Checks

• python3 -m py_compile scripts/sync_agent_config.py dashboard/court_discuss.py tests/test_sync_agent_config.py tests/test_minimax_model_config.py
• .venv/bin/python -m pytest tests/test_sync_agent_config.py tests/test_minimax_model_config.py -v (6 passed)
• .venv/bin/python -m pytest tests/ -v (66 passed, 7 unrelated existing failures in kanban and symlink tests)
• Parameter consistency assertions for both model IDs and all regional endpoints
• git diff --check