docs: Update documentation for v2.0 module reorganization

- Update feature_registry.json paths to new module locations (v0.3.0)
- Update cheatsheet with new import paths (v2.3)
- Mark migration plan as completed (v3.0)

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

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

.claude/skills/modules/OPTIMIZATION_ENGINE_MIGRATION_PLAN.md

@@ -2,15 +2,42 @@
 
 ## Complete Guide for Safe Codebase Restructuring
 
-**Document Version**: 2.1 (EXHAUSTIVE + CONTEXT ENGINEERING ALIGNED)
+**Document Version**: 3.0 (COMPLETED)
 **Created**: 2025-12-23
-**Updated**: 2025-12-28
-**Status**: READY FOR EXECUTION
+**Updated**: 2025-12-29
+**Status**: ✅ COMPLETED - Merged to main
 **Risk Level**: HIGH - Affects 500+ files across entire codebase
 **Next Phase**: ATOMIZER_CONTEXT_ENGINEERING_PLAN.md (execute AFTER this migration)
 
 ---
 
+## ✅ Migration Completed: 2025-12-29
+
+### Final Statistics
+| Metric | Value |
+|--------|-------|
+| Files modified | 120 |
+| Import changes | ~200 |
+| Commits | 2 (pre-migration checkpoint + migration) |
+| Branch | `refactor/optimization-engine-v2` merged to `main` |
+| Version bump | `optimization_engine` v1.0 → v2.0.0 |
+
+### Key Changes Made
+1. Created new directory structure: `core/`, `processors/surrogates/`, `nx/`, `study/`, `reporting/`, `config/`
+2. Moved 60+ Python files to new locations
+3. Updated all imports across 125 files
+4. Added lazy-loading `__init__.py` files to avoid circular imports
+5. Implemented backwards compatibility layer with deprecation warnings
+6. Updated `feature_registry.json` paths
+
+### Post-Migration Notes
+- All existing `run_optimization.py` scripts continue to work
+- Old imports emit deprecation warnings but still function
+- Dashboard integration preserved
+- Study databases unchanged
+
+---
+
 ## Execution Order (IMPORTANT)
 
 This migration plan should be executed **BEFORE** the Context Engineering plan.