Reorganize: Move all skills to skills/ folder

- Created skills/ directory
- Moved 272 skills to skills/ subfolder
- Kept agents/ at root level
- Kept installation scripts and docs at root level

Repository structure:
- skills/           - All 272 skills from skills.sh
- agents/           - Agent definitions
- *.sh, *.ps1       - Installation scripts
- README.md, etc.   - Documentation

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

skills/plugins/marketplaces/design-plugins/.claude-plugin/marketplace.json

@@ -0,0 +1,15 @@
+{
+  "name": "design-plugins",
+  "description": "Design exploration plugins for Claude Code",
+  "owner": {
+    "name": "0xdesigner"
+  },
+  "plugins": [
+    {
+      "name": "design-and-refine",
+      "source": "./design-and-refine",
+      "description": "Generate UI variations, collect feedback, synthesize the best elements, and iterate to confident design decisions",
+      "version": "0.1.0"
+    }
+  ]
+}