genviral Partner API Skill

> **TL;DR:** Wraps genviral's Partner API into 50+ bash commands. Core flow: `get-pack` → analyze images (metadata + vision) → `generate` with `pinned_images` → `render` → visual review (hard gate) → `create-post` → log to `workspace/performance/log.json`. Studio AI: `studio-models` → `studio-generate-image` (sync) or `studio-generate-video` → `studio-video-status --poll` (async). Auth via `GENVIRAL_API_KEY`. Config in `defaults.yaml`. Instance data in `workspace/`.