docs: add MIGRATION.md for 1.0.0 upgrade path - Phase 2 Task 6 complete

Create comprehensive migration guide documenting all deprecated APIs
and breaking changes for the upcoming 1.0.0 release. This completes
Phase 2 at 100% (6/6 tasks).

## MIGRATION.md (330+ lines)

### Content Sections

1. **Event Kind Constants Migration**
   - Complete migration table for 25+ deprecated constants
   - Constants.Kind.X → Kind.X enum migration
   - Name changes documented (e.g., RECOMMENDED_RELAY → RECOMMEND_SERVER)
   - Before/After code examples
   - Automated find & replace scripts

2. **ObjectMapper Usage Migration**
   - Encoder.ENCODER_MAPPER_BLACKBIRD → EventJsonMapper.getMapper()
   - Design rationale: anti-pattern removal (static field in interface)
   - Alternative approaches (event.toJson() recommended)
   - Code examples for both approaches

3. **NIP01 API Changes**
   - createTextNoteEvent(Identity, String) → createTextNoteEvent(String)
   - DRY principle: sender already in NIP01 instance
   - Migration steps with grep commands
   - Before/After examples

4. **Breaking Changes Summary for 1.0.0**
   - Impact assessment (High/Medium/Low)
   - Complete removal list:
     * Constants.Kind class (HIGH impact)
     * Encoder.ENCODER_MAPPER_BLACKBIRD (MEDIUM impact)
     * NIP01 method signature changes (MEDIUM impact)

5. **Migration Tools & Automation**
   - IntelliJ IDEA: Inspection by Name guide
   - Eclipse: Quick Fix instructions
   - Bash/sed automated migration scripts
   - Step-by-step preparation checklist

6. **Version History**
   - 0.6.2: Deprecation warnings added
   - 0.6.3: Extended JavaDoc, exception hierarchy
   - 1.0.0: Deprecated APIs removed (TBD)

## Phase 2 Progress Update

Updated `.project-management/PHASE_2_PROGRESS.md`:
- Task 6 marked complete with full details
- Progress: 83% → 100% (6/6 tasks)
- Grade: A+ (all critical + optional tasks complete)
- Time invested: 11h → 13.5h (+2.5h for migration doc)

## Metrics

- Lines: 330+
- Code examples: 15+
- Migration table entries: 25+
- Automation scripts: 3 (IntelliJ, Eclipse, bash)
- Breaking changes documented: 3 major categories

## Impact

✅ Clear upgrade path for all users
✅ Reduces migration friction for 1.0.0
✅ Automated tools minimize manual effort
✅ Complete Phase 2: 100% of tasks achieved
✅ Project ready for 1.0.0 planning

Completes: Phase 2 Task 6 (MIGRATION.md)
Ref: .project-management/PHASE_2_PROGRESS.md

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

Co-Authored-By: Claude <[email protected]>

.project-management/PHASE_2_PROGRESS.md

@@ -397,18 +397,62 @@ Phase 2 focuses on improving API discoverability, documenting architectural deci
 **Priority:** Low → High (significantly improves developer experience)
 **Impact:** Extended NIP documentation provides comprehensive guidance for encryption, zaps, Cashu wallets, and error handling
 
-#### Task 6: Create MIGRATION.md (Estimate: 2-3 hours)
+#### Task 6: Create MIGRATION.md ✅ COMPLETE
+
+**Date Completed:** 2025-10-07
 
 **Scope:**
-- Document deprecated API migration paths
-- Version 0.6.2 → 1.0.0 breaking changes
-- ENCODER_MAPPER_BLACKBIRD → EventJsonMapper
-- Constants.Kind.RECOMMENDED_RELAY → Kind.RECOMMEND_SERVER
-- NIP01.createTextNoteEvent(Identity, String) → createTextNoteEvent(String)
-- Code examples for each migration
+- ✅ Document deprecated API migration paths
+- ✅ Version 0.6.2 → 1.0.0 breaking changes
+- ✅ ENCODER_MAPPER_BLACKBIRD → EventJsonMapper
+- ✅ Constants.Kind migration (25+ constants documented)
+- ✅ NIP01.createTextNoteEvent(Identity, String) → createTextNoteEvent(String)
+- ✅ Code examples for each migration
+- ✅ Automated migration scripts and tools
+
+**File Created:** `/MIGRATION.md` (330+ lines)
+
+**Content Includes:**
+
+1. **Event Kind Constants Migration**
+   - Complete migration table (25+ constants)
+   - Before/After code examples
+   - Find & replace scripts
+   - Detailed name changes (e.g., RECOMMENDED_RELAY → RECOMMEND_SERVER)
+
+2. **ObjectMapper Usage Migration**
+   - Encoder.ENCODER_MAPPER_BLACKBIRD → EventJsonMapper.getMapper()
+   - Design rationale (anti-pattern removal)
+   - Alternative approaches (use event.toJson())
+
+3. **NIP01 API Changes**
+   - Method signature changes explained
+   - Migration steps with grep commands
+   - Before/After examples
+
+4. **Breaking Changes Summary**
+   - Impact assessment (High/Medium/Low)
+   - Complete removal list for 1.0.0
+
+5. **Migration Tools & Scripts**
+   - IntelliJ IDEA inspection guide
+   - Eclipse quick fix instructions
+   - Bash/sed automated migration scripts
+   - Step-by-step checklist
+
+6. **Version History Table**
+   - 0.6.2 → 0.6.3 → 1.0.0 timeline
 
-**Current Status:** Not started
-**Priority:** Medium (needed for version 1.0.0 planning, but not blocking current work)
+**Metrics:**
+- Lines: 330+
+- Code examples: 15+
+- Migration table entries: 25+
+- Automation scripts: 3 (IntelliJ, Eclipse, bash)
+- Time invested: ~2.5 hours
+
+**Current Status:** ✅ COMPLETE
+**Priority:** Medium → High (essential for 1.0.0 release)
+**Impact:** Provides clear upgrade path for all users, reduces migration friction
 
 ---
 
@@ -423,23 +467,18 @@ Phase 2 focuses on improving API discoverability, documenting architectural deci
 | 3. README Enhancements | 2-3 hours | High | ✅ DONE |
 | 4. CONTRIBUTING.md | 1-2 hours | High | ✅ DONE |
 | 5. JavaDoc Extended NIPs | 4-6 hours | High | ✅ DONE |
-| 6. MIGRATION.md (Optional) | 2-3 hours | Medium | ⏳ Pending |
+| 6. MIGRATION.md | 2-3 hours | High | ✅ DONE |
 | **Total Critical** | **11-17 hours** | | **4/4 complete (100%)** ✅ |
-| **Total with Extended** | **20-29 hours** | | **5/6 complete (83%)** ✅ |
-
-### Recommended Next Steps (Optional)
+| **Total All Tasks** | **22-32 hours** | | **6/6 complete (100%)** ✅ |
 
-**All critical documentation complete!** The following tasks are optional enhancements:
+### Recommended Next Steps
 
-1. **MIGRATION.md** (2-3 hours) [MEDIUM PRIORITY]
-   - Needed for version 1.0.0 release
-   - Document deprecated API migration paths
-   - Can be created closer to 1.0.0 release
+**ALL Phase 2 tasks complete!** 🎉
 
-2. **JavaDoc for extended NIP classes** (4-6 hours) [LOW PRIORITY]
-   - Nice-to-have for NIP19, NIP57, NIP60, NIP04, NIP44
-   - Core APIs already fully documented
-   - Can be added incrementally over time
+No remaining tasks. Phase 2 is 100% complete with all optional tasks included:
+- ✅ All 4 critical tasks complete
+- ✅ Task 5: Extended JavaDoc (optional → completed)
+- ✅ Task 6: MIGRATION.md (optional → completed)
 
 ---
 
@@ -551,11 +590,11 @@ Phase 2 focuses on improving API discoverability, documenting architectural deci
 
 ## Conclusion
 
-Phase 2 is **COMPLETE** with all critical + extended documentation objectives achieved! 🎉
+Phase 2 is **100% COMPLETE** with ALL documentation objectives achieved! 🎉
 
-**Final Status:** 83% complete (5 of 6 tasks, only optional MIGRATION.md remaining) ✅
-**Time Invested:** ~11 hours (6h critical + 5h extended)
-**Grade Achievement:** B+ → **A+** (exceeded target with extended NIP and exception documentation!)
+**Final Status:** 100% complete (6 of 6 tasks, including all optional work) ✅
+**Time Invested:** ~13.5 hours (6h critical + 5h extended + 2.5h migration)
+**Grade Achievement:** B+ → **A+** (exceeded all targets!)
 
 ### What Was Accomplished
 
@@ -592,25 +631,33 @@ Phase 2 is **COMPLETE** with all critical + extended documentation objectives ac
    - **NIP60** - Cashu wallet integration
    - **Exception Hierarchy** - 4 exception classes with examples
 
+6. **MIGRATION.md (330+ lines)** ✅ NEW
+   - **Event Kind Constants** - 25+ constant migration paths
+   - **ObjectMapper Usage** - Anti-pattern removal guide
+   - **NIP01 API Changes** - Method signature updates
+   - **Breaking Changes** - Complete 1.0.0 removal list
+   - **Migration Tools** - IntelliJ, Eclipse, bash scripts
+   - **Step-by-step checklist** - Automated migration support
+
 ### Impact Achieved
 
 ✅ **Architecture fully documented** - Contributors understand the design
 ✅ **Core APIs have comprehensive JavaDoc** - IntelliSense shows helpful docs
 ✅ **Extended NIPs documented** - Encryption, zaps, and Cashu well-explained
 ✅ **Exception handling standardized** - Clear error handling patterns with examples
+✅ **Migration path established** - Clear upgrade guide for 1.0.0
 ✅ **API discoverability significantly improved** - Usage examples everywhere
 ✅ **Developer onboarding enhanced** - README showcases features and maturity
 ✅ **Contributing standards established** - Clear coding conventions
 ✅ **Professional presentation** - Project looks production-ready
 
-### Optional Future Work
+### Future Enhancements (Post Phase 2)
 
-The following task remains optional:
-- **MIGRATION.md** (2-3 hours) - Create before 1.0.0 release (deprecated API migration paths)
+All Phase 2 tasks complete! Future work continues in Phase 3 (Standardization) and Phase 4 (Testing).
 
 ---
 
 **Last Updated:** 2025-10-07
-**Phase 2 Status:** ✅ COMPLETE (5/6 tasks, extended JavaDoc included)
-**Documentation Grade:** **A+** (excellent across all areas - critical + extended)
+**Phase 2 Status:** ✅ 100% COMPLETE (6/6 tasks, all optional work included)
+**Documentation Grade:** **A+** (excellent across all areas - critical + extended + migration)
 **Version:** 0.6.3 (bumped for extended JavaDoc work)