Add Mucha Image Studio skill

[alwaysmavs]

Summary

Adds mucha-gpt-image-studio, an Art Nouveau image-direction skill for original and reference-guided GPT Image 2 artwork.

What changed

• Added the agent runbook for Mucha-inspired avatars, pet portraits, posters, menus, invitations, social backgrounds, and wallpapers.
• Added English and Simplified Chinese user documentation modeled on the repository's video subtitle skill documentation.
• Added an OpenAI agent manifest and local skill metadata.
• Added the skill to the English and Simplified Chinese repository indexes.

Workflow and behavior

The skill selects text-to-image generation for written briefs and reference-guided editing for supplied person, pet, object, or product photos. It delegates execution to the existing gpt-image-2 companion skill so image upload, session persistence, polling, recovery, result parsing, and artifact download remain deterministic. The documentation calls out that this companion dependency must be installed.

Validation

• Ran oo skills validate skills/mucha-gpt-image-studio successfully.
• Ran git diff --check successfully.
• Verified the local GPT Image 2 companion runner interface and the Fusion API generation/edit action schemas without submitting an additional paid image job.