feat(docs): complete P2.6 type safety cleanup and P2.7 system invariants

P2.6: Type Safety Cleanup
- Replaced 'any' return types in vite-plugin.ts with concrete types (UserConfig, transform return type)
- Documented TypeScript mixin 'any[]' exception in PlatformServiceMixin.ts
- Audit confirmed: zero 'any' in codebase except documented TS mixin limitation
- All external boundaries use 'unknown', all data payloads use 'Record<string, unknown>'

P2.7: System Invariants Documentation
- Created SYSTEM_INVARIANTS.md documenting all 6 enforced invariants
- Added to docs/00-INDEX.md under Policy & Contracts section
- Each invariant includes: What, Why, How, Where

Progress Docs Updates:
- Updated 00-STATUS.md: marked P2.6/P2.7 complete, added type safety invariant note
- Updated 01-CHANGELOG-WORK.md: added 2025-12-22 entries for P2.6/P2.7
- Updated 03-TEST-RUNS.md: added P2.6 type safety audit test run
- Updated P2-DESIGN.md: marked P2.6 acceptance criteria complete
- Updated SYSTEM_INVARIANTS.md: added Type Safety Notes section

Baseline Tag:
- Created v1.0.11-p0-p1.4-p1.5-p2.6-p2.7-complete

TypeScript compilation: ✅ PASSES
Build: ✅ PASSES
CI: ✅ All checks pass

docs/progress/04-PARITY-MATRIX.md

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+# iOS vs Android Feature Parity Matrix
+
+**Purpose:** Feature-by-feature comparison of iOS and Android implementations to track parity gaps.  
+**Owner:** Development Team  
+**Last Updated:** 2025-12-22  
+**Status:** active
+
+---
+
+## Storage & Persistence
+
+| Feature | Android | iOS | Notes |
+|---------|---------|-----|-------|
+| Persistent state | ✅ SQLite (Room) | ✅ CoreData + SQLite | Both implemented |
+| Schema versioning | ✅ Room migrations | ⚠️ Partial | iOS has CoreData auto-migration, but explicit versioning may be needed |
+| State survives app restart | ✅ Yes | ✅ Yes | Both implemented |
+| State survives OS kill | ✅ Yes | ✅ Yes | Both implemented |
+| State survives reboot | ✅ Yes | N/A | iOS handles notifications automatically |
+
+---
+
+## Notification Scheduling
+
+| Feature | Android | iOS | Notes |
+|---------|---------|-----|-------|
+| Exact alarms | ✅ AlarmManager | N/A | iOS uses UNUserNotificationCenter |
+| Daily rollover | ✅ Automatic | ✅ Automatic | Both implemented (iOS uses NotificationCenter pattern) |
+| Schedule persistence | ✅ Database | ✅ UNUserNotificationCenter | iOS OS-guaranteed |
+| Next notification retrieval | ✅ getNotificationStatus() | ✅ getNotificationStatus() | Both implemented |
+
+---
+
+## Recovery & Resilience
+
+| Feature | Android | iOS | Notes |
+|---------|---------|-----|-------|
+| App launch recovery | ✅ ReactivationManager | ✅ ReactivationManager | Both implemented with persistence |
+| Boot recovery | ✅ BootReceiver | N/A | iOS handles automatically |
+| Missed notification detection | ✅ Yes | ✅ Yes | Both implemented with persistent state |
+| Recovery logging | ✅ Comprehensive | ✅ Comprehensive | Both have good logging |
+| Invalid data recovery | ✅ Tested (TEST 4) | ✅ Tested (RecoveryTests) | Both have automated recovery tests |
+| Rollover idempotency | ✅ Tested | ✅ Tested | Both verify duplicate rollover prevention |
+| Migration safety | ✅ Tested | ✅ Tested | Both test unknown/missing fields |
+
+---
+
+## Background Execution
+
+| Feature | Android | iOS | Notes |
+|---------|---------|-----|-------|
+| Background fetch | ✅ WorkManager | ✅ BGTaskScheduler | Both implemented |
+| Background notification | ✅ WorkManager | ✅ BGTaskScheduler | Both implemented |
+| Execution time limits | ✅ Flexible | ⚠️ ~30 seconds | iOS has strict limits |
+| Battery optimization handling | ✅ Documented | N/A | iOS handles automatically |
+
+---
+
+## Error Handling
+
+| Feature | Android | iOS | Notes |
+|---------|---------|-----|-------|
+| Error codes | ✅ Structured | ✅ Structured | Both have error codes |
+| Error recovery | ✅ Yes | ✅ Yes | Both handle errors gracefully |
+| Invalid data handling | ✅ Recovery tested | ⚠️ Input validation only | **GAP** - iOS needs recovery testing |
+
+---
+
+## Testing
+
+| Feature | Android | iOS | Notes |
+|---------|---------|-----|-------|
+| Unit tests | ✅ Yes | ⚠️ Partial | iOS has some tests |
+| Integration tests | ✅ Yes | ⚠️ Partial | iOS has some tests |
+| Test automation | ✅ High | ⚠️ Medium | iOS has manual components |
+| Recovery testing | ✅ Yes | ✅ Yes | Both have automated recovery tests (DailyNotificationRecoveryTests.swift) |
+
+---
+
+## Summary
+
+### Critical Gaps (P0)
+
+**None** - All critical gaps addressed:
+- ✅ iOS rollover implemented (NotificationCenter pattern)
+- ✅ iOS recovery testing implemented (DailyNotificationRecoveryTests.swift)
+- ✅ iOS persistence confirmed (CoreData + SQLite)
+
+### Important Gaps (P1)
+
+1. **Schema Versioning** - iOS has CoreData auto-migration, but explicit versioning strategy may be needed
+2. **Test Automation** - iOS tests can be run via xcodebuild, but CI integration may need macOS runners
+
+### Nice-to-Have (P2)
+
+1. **Combined Edge Case Tests** - DST boundary + duplicate delivery + cold start combined scenario
+2. **OS Reboot Testing** - True OS reboot scenarios (iOS handles automatically, but explicit testing may be valuable)
+
+---
+
+**Last Updated:** 2025-12-16  
+**Next Review:** After PHASE 2 completion
+