more detailed SDLC plan

_docs/00_templates/feature_parity_checklist.md

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+# Feature Parity Checklist
+
+Use this checklist to ensure all functionality is preserved during refactoring.
+
+---
+
+## Project: [Project Name]
+## Refactoring Scope: [Brief description]
+## Date: [YYYY-MM-DD]
+
+---
+
+## Feature Inventory
+
+### API Endpoints
+
+| Endpoint | Method | Before | After | Verified |
+|----------|--------|--------|-------|----------|
+| /api/v1/example | GET | Working | | [ ] |
+| | | | | [ ] |
+
+### Core Functions
+
+| Function/Module | Purpose | Before | After | Verified |
+|-----------------|---------|--------|-------|----------|
+| | | Working | | [ ] |
+| | | | | [ ] |
+
+### User Workflows
+
+| Workflow | Steps | Before | After | Verified |
+|----------|-------|--------|-------|----------|
+| User login | 1. Enter credentials 2. Submit | Working | | [ ] |
+| | | | | [ ] |
+
+### Integrations
+
+| External System | Integration Type | Before | After | Verified |
+|-----------------|------------------|--------|-------|----------|
+| | API/Webhook/DB | Working | | [ ] |
+| | | | | [ ] |
+
+---
+
+## Behavioral Parity
+
+### Input Handling
+- [ ] Same inputs produce same outputs
+- [ ] Error messages unchanged (or improved)
+- [ ] Validation rules preserved
+- [ ] Edge cases handled identically
+
+### Output Format
+- [ ] Response structure unchanged
+- [ ] Data types preserved
+- [ ] Null handling consistent
+- [ ] Date/time formats preserved
+
+### Side Effects
+- [ ] Database writes produce same results
+- [ ] File operations unchanged
+- [ ] External API calls preserved
+- [ ] Event emissions maintained
+
+---
+
+## Non-Functional Parity
+
+### Performance
+- [ ] Response times within baseline +10%
+- [ ] Memory usage within baseline +10%
+- [ ] CPU usage within baseline +10%
+- [ ] No new N+1 queries introduced
+
+### Security
+- [ ] Authentication unchanged
+- [ ] Authorization rules preserved
+- [ ] Input sanitization maintained
+- [ ] No new vulnerabilities introduced
+
+### Reliability
+- [ ] Error handling preserved
+- [ ] Retry logic maintained
+- [ ] Timeout behavior unchanged
+- [ ] Circuit breakers preserved
+
+---
+
+## Test Coverage
+
+| Test Type | Before | After | Status |
+|-----------|--------|-------|--------|
+| Unit Tests | X pass | | [ ] Same or better |
+| Integration Tests | X pass | | [ ] Same or better |
+| E2E Tests | X pass | | [ ] Same or better |
+
+---
+
+## Verification Steps
+
+### Automated Verification
+1. [ ] All existing tests pass
+2. [ ] No new linting errors
+3. [ ] Coverage >= baseline
+
+### Manual Verification
+1. [ ] Smoke test critical paths
+2. [ ] Verify UI behavior (if applicable)
+3. [ ] Test error scenarios
+
+### Stakeholder Sign-off
+- [ ] QA approved
+- [ ] Product owner approved (if behavior changed)
+
+---
+
+## Discrepancies Found
+
+| Feature | Expected | Actual | Resolution | Status |
+|---------|----------|--------|------------|--------|
+| | | | | |
+
+---
+
+## Notes
+- Any intentional behavior changes must be documented and approved
+- Update this checklist as refactoring progresses
+- Keep baseline metrics for comparison
+