docs: Update marketplace URL format to full GitHub URL

- Update plugin marketplace add command from 'daymade/claude-code-skills' to full GitHub URL
- Add marketplace name clarification (daymade-skills from marketplace.json)
- Update all plugin install commands to use @daymade-skills suffix
- Standardize marketplace references across all documentation files
- Update installation scripts to use new URL format

Affected files:
- CLAUDE.md: Development commands and skill creation workflow
- CONTRIBUTING.md: Contribution guidelines
- QUICKSTART.md: Quick start guide
- QUICKSTART.zh-CN.md: Chinese quick start guide
- README.md: Main documentation
- README.zh-CN.md: Chinese documentation
- demos/index.html: Demo page
- scripts/install.ps1: Windows installation script
- scripts/install.sh: Unix installation script

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

demos/index.html

@@ -548,7 +548,7 @@
             <p>Install the Claude Code Skills Marketplace and start using these skills today!</p>
             <br>
             <p><strong>Quick Install:</strong></p>
-            <p><code>/plugin marketplace add daymade/claude-code-skills</code></p>
+            <p><code>/plugin marketplace add https://github.com/daymade/claude-code-skills</code></p>
             <br>
             <p>
                 <a href="https://github.com/daymade/claude-code-skills" target="_blank">📖 Documentation</a> |