Plugin marketplace: third-party adapters + viewers

## Что это Идея: расширить skills marketplace (E04) до полноценного plugin marketplace, где community может публиковать: - Custom source adapters (Notion, Linear, Jira, ClickUp, etc.) - Custom artifact viewers (GraphQL schema viewer, Kubernetes manifest viewer, etc.) - Custom automation triggers - Custom UI themes/skins - Custom AAP handlers Publishing flow: developer signs plugin Ed25519 → submits manifest к registry → CI runs security checks (sandbox-eval, permission audit, manifest validation) → merged → discoverable in marketplace. Revenue split optional для paid plugins (community decides). Security model: plugins runs в isolated process с capability-based permissions. Default deny — пользователь explicitly grants каждый scope. ## Зачем Marketplace без third-party content — это just registry. Vibrant ecosystem requires authors могут monetize и users могут discover. Sandbox-based security делает open marketplace safe-by-default. ## Источники вдохновения - [kunkunsh/kunkun](https://github.com/kunkunsh/kunkun) — extensible plugin launcher с sandboxed exec - [Tencent/xLua](https://github.com/Tencent/xLua) — embedded scripting sandbox - [LiveContainer/LiveContainer](https://github.com/LiveContainer/LiveContainer) — iOS app sandboxing для plugin runtime