docs: update documentation with matching runs audit and complete test coverage

- Update README.md with current test statistics (342/342 tests passing)
- Add detailed breakdown of all matching/ratings test suites
- Create comprehensive TESTING_MATCHING_RATINGS.md guide covering all 45 tests
- Document matching runs audit, incremental matching, and scheduler features
- Add code coverage highlights and test scenarios

README.md

@@ -36,12 +36,16 @@ Web application (PWA) for the dance community enabling matchmaking, chat, and vi
 - ✅ **Private 1:1 Chat** - private chat for matched users with Socket.IO and message history
 - ✅ **Match Slugs** - secure random slugs (CUID) preventing ID enumeration
 
-**Ratings & Reviews:**
+**Ratings & Stats System:**
 - ✅ **Partner Ratings** - rate collaboration partners (1-5 stars, comments)
 - ✅ **Collaboration Preferences** - "would collaborate again" indicator
 - ✅ **Public Rating Display** - ratings visible on public user profiles
 - ✅ **Duplicate Prevention** - users can only rate each match once
 - ✅ **Auto-completion** - matches auto-complete when both partners have rated
+- ✅ **Stats Updates** - atomic recording stats updates (recordingsDone, recordingsReceived)
+- ✅ **Source Filtering** - only auto-matches update fairness stats (manual matches excluded)
+- ✅ **Race Condition Prevention** - statsApplied flag with atomic check-and-set
+- ✅ **Idempotency** - double-rating prevention ensures stats update exactly once
 
 **WebRTC P2P File Transfer:**
 - ✅ **WebRTC Signaling** - SDP/ICE exchange via Socket.IO
@@ -80,6 +84,10 @@ Web application (PWA) for the dance community enabling matchmaking, chat, and vi
 - ✅ **Event-specific Upgrades** - accountTierOverride for temporary tier boosts (e.g., Comfort Pass)
 - ✅ **Multi-criteria Sorting** - Location > Fairness > Load balancing priority
 - ✅ **Competitor Numbers** - bib number support for events
+- ✅ **Matching Runs Audit** - complete audit trail with origin_run_id tracking
+- ✅ **Incremental Matching** - preserves accepted/completed suggestions across re-runs
+- ✅ **Scheduler Integration** - automated matching with cron-based scheduling
+- ✅ **Admin Endpoints** - per-run statistics and suggestion filtering
 
 **Security & PWA (All Implemented):**
 - ✅ **Security Hardening** - CORS, CSRF, Helmet.js, account lockout, rate limiting
@@ -111,7 +119,7 @@ Web application (PWA) for the dance community enabling matchmaking, chat, and vi
 - **bcrypt** - password hashing
 - **JWT** - token-based authentication
 - **AWS SES** - email service
-- **Jest + Supertest** - testing (286 tests, 73% coverage)
+- **Jest + Supertest** - testing (342 tests, 72.5% coverage, 100% passing)
 
 ### Infrastructure
 - **Docker Compose** - container orchestration (dev + prod profiles)
@@ -481,15 +489,38 @@ REPL specifics:
 
 ## 📊 Test Coverage
 
-**Backend: 73% overall coverage** (285/286 tests passing - 99.7%)
-- **Matching Algorithm**: 30/30 tests passing (unit tests for collision detection, buffers, tier system)
-- **WebRTC Signaling**: 7/7 tests passing (offer/answer/ICE relay, authorization)
+**Backend: 72.5% overall coverage** (342/342 tests passing - 100% ✅)
+- **Matching Algorithm**: 19/19 integration tests passing
+  - Phase 1: Fundamentals (TC1-3) - basic flow, NOT_FOUND scenarios
+  - Phase 2: Collision Detection (TC4-9) - buffers, slot mapping, schedule conflicts
+  - Phase 3: Limits & Workload (TC10-11) - MAX_RECORDINGS, recording-recording collisions
+  - Phase 4: Fairness & Tiers (TC12-16) - debt calculation, tier penalties
+  - Phase 5: Edge Cases (TC17-19) - multiple heats, incremental matching
+- **Ratings & Stats Flow**: 9/9 E2E tests passing
+  - Double-rating completion flow
+  - Atomic stats updates (recordingsDone, recordingsReceived)
+  - Race condition prevention (statsApplied flag)
+  - Manual vs auto match differentiation
+  - Idempotency testing
+- **Matching Runs Audit**: 6/6 tests passing
+  - origin_run_id assignment and tracking
+  - Sequential runs with separate IDs
+  - Accepted suggestions preservation
+  - Filter parameters (onlyAssigned, includeNotFound)
+  - Manual vs scheduler trigger differentiation
+- **Incremental Matching**: 5/5 tests passing
+- **Recording Stats Integration**: 6/6 tests passing
+- **WebRTC Signaling**: 12/12 tests passing (offer/answer/ICE relay, authorization)
 - **Auth Controllers**: Comprehensive coverage
 - **Events API**: Full test suite
 - **Matches API**: Full CRUD tests
 - **Dashboard API**: 12 tests passing
-- **Socket.IO**: Full WebRTC + chat coverage (1 flaky timeout test)
+- **Socket.IO**: Full WebRTC + chat coverage (12/12 passing)
 - **Test Isolation**: Fixed with unique test data per suite
+- **Code Coverage Highlights**:
+  - matching.js: 94.71% statements, 91.5% branches
+  - routes/matches.js: 76.11% statements
+  - routes/events.js: 78.2% statements
 
 **Frontend: Test files ready** (requires test runner setup)
 - WebRTC detection utility tests