docs: Fix documentation inconsistencies and version references

- Fix version numbers: Changed 4.0.x to 2.0.x in SECURITY.md
- Fix CHANGELOG.md: Changed SuperClaude v4.0.0 to v1.0.0
- Add missing /task command to README.md command list
- Remove non-existent validate-references.sh from CONTRIBUTING.md
- Clarify installation paths (files go to ~/.claude/ not project dir)
- Add MCP server installation notice to README.md
- Ensure consistent v2.0.1 references across all docs

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

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

SECURITY.md

@@ -4,8 +4,8 @@
 
 | Version | Supported |
 |---------|-----------|
-| 4.0.x   | ✅ Yes    |
-| < 4.0   | ❌ No     |
+| 2.0.x   | ✅ Yes    |
+| < 2.0   | ❌ No     |
 
 ## Reporting Security Vulnerabilities