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

[octo-patch]

Summary

• Add MiniMax-AI/cli to skills.json so the mmx-cli skill is discoverable out of the box
• References the external repo at https://github.com/MiniMax-AI/cli (same pattern as existing camera-claw entry)
• Skill updates are fully decoupled: MiniMax maintains the upstream SKILL.md, no changes needed in this project

31 lines added, 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

• skills.json is valid JSON (verified with python3 -c "import json; json.load(open('skills.json'))")
• New entry follows the same external-repo pattern as camera-claw
• No existing skills are modified