docs(skills): add MiniMax-AI/cli as default skill tap

[octo-patch]

Summary

• Add MiniMax-AI/cli to the Skills 来源 section in docs/agents/skills-management.md so mmx-cli is discoverable out of the box
• Users can install via the remote install panel using MiniMax-AI/cli as source — the SKILL.md is fetched directly from MiniMax-AI/cli
• Skill updates are fully decoupled: MiniMax maintains the upstream SKILL.md, no changes needed in this project

1 line changed, 0 new files.

What is mmx-cli?

mmx-cli is a CLI tool for the MiniMax AI platform, providing:

• Text generation (MiniMax-M2.7 model)
• Image generation (image-01)
• Video generation (Hailuo-2.3)
• Speech synthesis (speech-2.8-hd, 300+ voices)
• Music generation (music-2.6, with lyrics, cover, and instrumental)
• Web search

The SKILL.md follows the agentskills.io standard.

Test plan

• Open Skills 管理页面 → 远程安装面板
• Enter MiniMax-AI/cli as source → click 查看可安装 Skills
• mmx-cli appears in the list and can be installed successfully