docs: fix image quality troubleshooting — clearer raise vs lower framing

Each entry now unambiguously describes the symptom and the direction:
- Split each threshold into two entries (problem in each direction)
- Eliminate ambiguous 'Face too small' and 'Low confidence detections included'

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Troubleshooting.md

@@ -161,8 +161,10 @@ Remove this after one run. It deletes winnow-managed Frigate training files for
 
 ## Image quality issues
 
-- **Too many blurry images selected**: Raise `BLUR_THRESHOLD` (default `120.0`) — higher values require sharper images; e.g. `200` is stricter
-- **Too many images rejected as blurry**: Lower `BLUR_THRESHOLD` — e.g. `80` accepts more blur
-- **Face too small**: Lower `MIN_FACE_WIDTH` (default `90px`)
-- **Low confidence detections included**: Raise `MIN_CONFIDENCE` (default `0.7`)
+- **Selected images are too blurry**: Raise `BLUR_THRESHOLD` (default `120.0`) — e.g. `200` requires sharper images
+- **Too many images rejected for blur**: Lower `BLUR_THRESHOLD` — e.g. `80` accepts blurrier images
+- **Too many images rejected for small face size**: Lower `MIN_FACE_WIDTH` (default `90`) — e.g. `50` accepts smaller face crops
+- **Selected images have poor-quality face crops**: Raise `MIN_FACE_WIDTH` — e.g. `150` requires larger face crops
+- **Too many images rejected for low detection confidence**: Lower `MIN_CONFIDENCE` (default `0.7`) — e.g. `0.5` accepts lower-confidence detections
+- **Training set includes marginal detections**: Raise `MIN_CONFIDENCE` — e.g. `0.85` requires more confident detections
 - **Rejected images being re-tried**: Set `RETRY_REJECTED=true` for one run