Fix recv_raw_column.py height mismatch and update script paths in docs

- Fixed HEIGHT from 480 to 640 to match actual videotestsrc output
- Added DEBUG flag to control debug output visibility
- Added cv2.namedWindow() for proper window initialization
- Updated all Python script references in markdown files to scripts/ folder
- Updated network_guide.md with correct frame dimensions and Python receiver option

network_guide.md

@@ -0,0 +1,29 @@
+# how to send a line
+
+## Sender (crop to first column, send raw over UDP)
+```pwsh
+gst-launch-1.0 -v `
+    videotestsrc pattern=smpte ! `
+    videocrop left=0 right=639 top=0 bottom=0 ! `
+    video/x-raw,format=RGB,width=1,height=640,framerate=30/1 ! `
+    udpsink host=127.0.0.1 port=5000
+```
+
+**Note:** Default `videotestsrc` height is 640, not 480. Adjust caps to match your actual frame size.
+
+## Receiver Options
+
+### GStreamer Receiver (raw UDP → display)
+```pwsh
+gst-launch-1.0 -v `
+    udpsrc port=5000 caps="video/x-raw,format=RGB,width=1,height=640,framerate=30/1" ! `
+    videoconvert ! `
+    autovideosink
+```
+
+### Python/OpenCV Receiver
+```pwsh
+uv run scripts/recv_raw_column.py
+```
+
+See [`scripts/recv_raw_column.py`](scripts/recv_raw_column.py) for the Python implementation with debug options.