feat(minimax): add MiniMax-M3, set as default, drop M2.5/M2.1/M2

- Add MINIMAX_M3 = "MiniMax-M3" constant and put it first in MODEL_LIST
- Default MinimaxBot model: MiniMax-M2.7 -> MiniMax-M3
- Keep MiniMax-M2.7 and MiniMax-M2.7-highspeed as legacy options
- Drop MINIMAX_M2_5 / MINIMAX_M2_1 / MINIMAX_M2_1_LIGHTNING / MINIMAX_M2
- Update web console recommended/provider model lists
- Update README capability table and docs/models index (en/zh/ja)
- Update docs/models/minimax.mdx and coding-plan.mdx MiniMax section
- Update run.sh / run.ps1 installer default and menu hint
- Update zh CLI status sample output
- Update unit tests to assert new M3 default and constant

TTS (speech-2.*) and API base URL remain unchanged.

README.md

@@ -102,7 +102,7 @@ CowAgent supports all mainstream LLM providers. **Chat, vision, image generation
 | [GLM](https://docs.cowagent.ai/models/glm) | glm-5.1, glm-5v-turbo | ✅ | ✅ | | ✅ | | ✅ |
 | [Doubao](https://docs.cowagent.ai/models/doubao) | doubao-seed-2.0 series | ✅ | ✅ | ✅ | | | ✅ |
 | [Kimi](https://docs.cowagent.ai/models/kimi) | kimi-k2.6 | ✅ | ✅ | | | | |
-| [MiniMax](https://docs.cowagent.ai/models/minimax) | MiniMax-M2.7 | ✅ | ✅ | ✅ | | ✅ | |
+| [MiniMax](https://docs.cowagent.ai/models/minimax) | MiniMax-M3 | ✅ | ✅ | ✅ | | ✅ | |
 | [ERNIE](https://docs.cowagent.ai/models/qianfan) | ernie-5.1 | ✅ | ✅ | | | | |
 | [MiMo](https://docs.cowagent.ai/models/mimo) | mimo-v2.5 / pro | ✅ | ✅ | | | ✅ | |
 | [LinkAI](https://docs.cowagent.ai/models/linkai) | One key for 100+ models | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ |