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

[octo-patch]

Summary

• Add MiniMax-AI/cli to resources/agents/core/skills/ so the mmx-cli skill is discoverable out of the box via Mysti's three-tier agent loading system
• Users can activate the skill by selecting it from the Skills panel — the skill description instructs agents to use the mmx CLI for media generation
• Skill updates are fully decoupled: MiniMax maintains the upstream SKILL.md at MiniMax-AI/cli, no changes needed in this project

1 file added, 0 existing files modified.

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 and includes agent-specific flags (--non-interactive, --quiet, --output json).

Test plan

• New mmx-cli skill appears in the Skills section of the Mysti sidebar
• Activation triggers (image generation, video, speech, minimax, etc.) surface the skill in autocomplete suggestions
• Existing skills and personas are unaffected (no existing files modified)