refactor: replace Code Index MCP with native CCW CodexLens

Migrate all Code Index MCP references to CCW's built-in CodexLens tool:
- Update context-search-agent with codex_lens API calls
- Update test-context-search-agent with new search patterns
- Update memory/load command file discovery reference
- Update context-gather and task-generate-tdd MCP capabilities
- Update INSTALL docs to reflect CodexLens as built-in feature
- Sync all mirrored files in skills/command-guide/reference/

Old API (mcp__code-index__*) → New API (mcp__ccw-tools__codex_lens)

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

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

INSTALL.md

@@ -171,9 +171,10 @@ MCP (Model Context Protocol) tools provide advanced codebase analysis. **Recomme
 | MCP Server | Purpose | Installation Guide |
 |------------|---------|-------------------|
 | **Exa MCP** | External API patterns & best practices | [Install Guide](https://smithery.ai/server/exa) |
-| **Code Index MCP** | Advanced internal code search | [Install Guide](https://github.com/johnhuang316/code-index-mcp) |
 | **Chrome DevTools MCP** | ⚠️ **Required for UI workflows** - URL mode design extraction | [Install Guide](https://github.com/ChromeDevTools/chrome-devtools-mcp) |
 
+> **Note**: Code Index MCP has been replaced by CCW's built-in **CodexLens** (`mcp__ccw-tools__codex_lens`). No additional installation required for code indexing.
+
 ⚠️ **Note**: Some workflows expect MCP tools to be available. Without them, you may experience:
 - Slower code analysis and search operations
 - Reduced context quality in some scenarios