docs(issue-14): add detailed Stage 4 plan - Final Coordination & Go/No-Go

Child #2 Pre-Migration Preparation - Stage 4 Planning Complete (FINAL STAGE)

Stage 4 Objective:
- Execute final GitHub Support coordination
- Lock migration timeline with stakeholder approval
- Complete comprehensive go/no-go validation
- Finalize Child #2 completion and Child #3 preparation

Implementation Plan:
- Step 4.1: GitHub Support Final Coordination (1.5h)
- Step 4.2: Migration Timeline Finalization (1h)
- Step 4.3: Complete Go/No-Go Validation (1h)
- Step 4.4: Child #2 Completion & Child #3 Preparation (0.5h)

Critical Success Factors:
- GitHub Support coordination confirmed with migration window
- Complete stakeholder approval with GO decision
- Child #2 100% completion with all deliverables
- Child #3 preparation checklist ready for execution

Files Added:
- 004-final-coordination-go-no-go.md (comprehensive 4-hour final stage plan)

Stage 4 Status: 📋 READY FOR EXECUTION
Target Completion: 2025-11-09 11:10 UTC
Child #2 Completion: Upon Stage 4 success
Next: Begin implementation execution

Related: #12, #14
Workflow Stage: Planning → Implementation (FINAL STAGE)

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

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

Author: InfoTech.io Bot