refactor: remove MCP code-index dependency, replace with ripgrep/find

Replace all mcp__code-index__ calls with native ripgrep and find commands
across workflow and command files for better performance and portability.

Changes:
- Remove 41 mcp__code-index__ function calls from 12 files
- Replace with ripgrep (rg) for content search
- Replace with find for file discovery
- Remove index refresh dependencies (no longer needed)

Modified files:
- workflow/tools: context-gather, test-context-gather, task-generate-agent,
  task-generate, test-task-generate (core workflow tools)
- workflow: review (security scanning)
- memory: load, update-related, docs (memory management)
- cli/mode: plan, bug-index, code-analysis (CLI modes)

Documentation updates:
- Simplify mcp-tool-strategy.md to only Exa usage (5 lines)
- Streamline context-search-strategy.md to 69 lines
- Standardize codebase-retrieval syntax per intelligent-tools-strategy.md

Benefits:
- Faster search with ripgrep (no index overhead)
- Better cross-platform compatibility
- Simpler configuration (fewer MCP dependencies)
- -232 lines of code removed

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

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

.claude/commands/workflow/review.md

@@ -92,10 +92,10 @@ After bash validation, the model takes control to:
 2. **Perform Specialized Review**: Based on `review_type`
 
    **Security Review** (`--type=security`):
-   - Use MCP code search for security patterns:
+   - Use ripgrep for security patterns:
      ```bash
-     mcp__code-index__search_code_advanced(pattern="password|token|secret|auth", file_pattern="*.{ts,js,py}")
-     mcp__code-index__search_code_advanced(pattern="eval|exec|innerHTML|dangerouslySetInnerHTML", file_pattern="*.{ts,js,tsx}")
+     rg "password|token|secret|auth" -g "*.{ts,js,py}"
+     rg "eval|exec|innerHTML|dangerouslySetInnerHTML" -g "*.{ts,js,tsx}"
      ```
    - Use Gemini for security analysis:
      ```bash