Docs: Update TESTING_STATUS.md with current metrics

- Updated test counts: 106 total, 104 passing, 2 skipped
- Updated signal counts: 21 (ensemble), 19 (statistical)
- Updated version: 6.0.0
- Added performance metrics
- Documented known limitations

docs/TESTING_STATUS.md

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+# Testing Status
+
+## Current Status
+- **Total Tests:** 106
+- **Passing:** 104
+- **Skipped:** 2
+- **Failing:** 0
+
+## Test Coverage
+
+### Detector Signal Counts
+- **Ensemble (Full System):** 21 signals
+  - Statistical: 19 signals
+  - DIRE: 1 signal
+  - CLIP: 1 signal
+
+- **Individual Detectors:**
+  - StatisticalDetector: 19 signals
+  - CovarianceDetector: 16 signals
+  - UltraAdvancedDetector: 13 signals
+  - AdvancedAIDetector: 10 signals
+
+### Version
+- **Current Version:** 6.0.0
+- **Last Updated:** March 9, 2026
+
+### Known Limitations
+- DIRE detector requires HuggingFace authentication in CI (graceful fallback implemented)
+- CLIP centroids are placeholder values until reference database is built (Issue #32)
+- Expected variance in AI probability: ~12-15% due to CLIP randomness
+
+### Test Performance
+- Fast tests (no ML models): ~2 minutes
+- Slow tests (ML model loading): ~3 minutes
+- Total: ~5 minutes
+
+Run fast tests only:
+```bash
+pytest backend/tests/ -m "not slow" -v
+```
+
+Run all tests:
+```bash
+pytest backend/tests/ -v
+```