feat(providers): add MiniMax model support

[octo-patch]

Purpose

• Add first-class MiniMax chat model configuration for MiniMax-M3 and MiniMax-M2.7.

Proposed Changes

• Add MiniMax model initialization with selectable chat protocol and region.
• Keep global and China endpoint sets in the public configuration.
• Read the API key from MINIMAX_API_KEY without overriding explicit client arguments.
• Update the generated and repository configuration, provider documentation, dependency lock, and rai_core minor version.
• Add focused tests for routing, endpoint selection, API-key handling, embeddings rejection, and captured request-path behavior.

Issues

• None.

Testing

• Passed: uv lock
• Passed: PYTHONPATH=src/rai_core python -m pytest tests/initialization/test_minimax_initialization.py -q
• Passed: PYTHONPATH=src/rai_core python -m pytest tests/initialization/test_model_initialization.py -q
• Passed: ruff check src/rai_core/rai/initialization/model_initialization.py src/rai_core/rai/initialization/config_initialization.py tests/initialization/test_minimax_initialization.py
• Passed: ruff format --check src/rai_core/rai/initialization/model_initialization.py src/rai_core/rai/initialization/config_initialization.py tests/initialization/test_minimax_initialization.py
• Passed: git diff --check
• Timed out after 600 seconds: uv sync --all-groups while installing optional dependency groups.