feat: consolidate marketplace skills into kyberforge plugin

Moves create-plugin, marketplace-architect, write-skill, and write-eval
from canonical .agents/skills/ into plugins/kyberforge/skills/, along
with all bundled sub-files, evals, and the plugin-marketplace-architecture
research doc. Bundles templates/plugin/ into create-plugin/assets/plugin-template/
so the skill is self-contained after install-time caching. Removes
templates/plugin/ and docs/research/plugin-marketplace-architecture.md
from the repo root as they are now exclusively in the plugin.

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

plugins/kyberforge/skills/marketplace-architect/META.md

@@ -0,0 +1,21 @@
+```yaml
+version: "1.0"
+updated: 2026-06-20
+
+when: >
+  Invoked when the user wants to create, manage, or maintain a plugin marketplace for
+  Claude Code and/or GitHub Copilot CLI. Covers four operations: (a) audit and refactor
+  a repository of skills/agents/hooks into a plugin marketplace layout, (b) adopt external
+  plugins/skills/agents from outside sources, (c) update and maintain an existing
+  marketplace.json and plugin manifests, (d) validate existing plugin manifests for naming,
+  structure, and cross-tool compatibility. Also triggered implicitly when the user asks
+  about distributing skills to a team, organizing loose skills into installable units, or
+  setting up cross-tool distribution — even without saying "marketplace".
+
+references:
+  - https://code.claude.com/docs/en/plugins
+  - https://code.claude.com/docs/en/plugin-marketplaces
+  - https://code.claude.com/docs/en/plugins-reference
+  - https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/plugins-creating
+  - https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/plugins-marketplace
+```