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.

docs/zh/cli/general.mdx

@@ -33,7 +33,7 @@ description: 查看状态、管理配置和上下文等常用命令
 Process: PID 12345 | Running 2h 15m
 Version: 2.0.4
 Channel: web
-Model:   MiniMax-M2.5
+Model:   MiniMax-M3
 Mode:    agent
 
 Session: 12 messages | 8 skills loaded