feat: add kyberforge plugin and rename plugin-create skill

Scaffolds the kyberforge marketplace management plugin (create-plugin and
marketplace-architect skills will live here). Renames the plugin-create
skill directory to create-plugin to match the canonical kebab-order convention.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/kyberforge/agents/kyberforge.agent.md

@@ -0,0 +1,13 @@
+---
+name: kyberforge
+description: Skills and agents for creating, maintaining, and managing a Claude Code / Copilot CLI plugin marketplace.
+tools:
+  - read_file
+  - list_directory
+---
+
+Replace this with your agent's system prompt and instructions.
+
+This file is loaded by **GitHub Copilot CLI**. The `tools:` frontmatter field declares
+which tools the agent can use — add or remove tools as needed.
+For Claude Code, see `kyberforge.md`.