feat: integrate MiniMax into model router, backend config, and common

common.py:
- Add minimax_chat → MiniMax/MiniMax-Text-01 to _BACKEND_DEFAULT_MODELS
- Add minimax/minimax_chat aliases to _BACKEND_ALIASES

backend_config.py:
- Add minimax_chat to set_optimizer_backend() valid set
- Add minimax_chat to set_target_backend() valid set
- Add minimax_chat to is_optimizer_chat_backend()
- Add minimax_chat to is_target_chat_backend()

__init__.py:
- Import minimax_backend as _minimax
- Add minimax_chat to set_backend() legacy handler
- Add minimax_chat to get_backend_name() reporting
- Route chat_target() and chat_target_messages() to _minimax
- Update NotImplementedError messages to list minimax_chat
- Aggregate _minimax into get_token_summary()
- Add _minimax.reset_token_tracker()
- Add configure_minimax_chat() delegator
- Add _minimax to set_reasoning_effort() and set_target_deployment()

skillopt/model/common.py

@@ -25,6 +25,7 @@ _BACKEND_DEFAULT_MODELS = {
     "claude_chat": "claude-sonnet-4-6",
     "claude_code_exec": "claude-sonnet-4-6",
     "qwen_chat": "Qwen/Qwen3.5-4B",
+    "minimax_chat": "MiniMax/MiniMax-Text-01",
 }
 
 _BACKEND_ALIASES = {
@@ -41,6 +42,8 @@ _BACKEND_ALIASES = {
     "anthropic": "claude_chat",
     "qwen": "qwen_chat",
     "qwen_chat": "qwen_chat",
+    "minimax": "minimax_chat",
+    "minimax_chat": "minimax_chat",
 }