docs(aerotech): live plot colours, stop_plot

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M8zoDzDfsCTY2o5bT3J7Wv

docs/user/saxs/aerotech_stages/aerotech_stages.md

@@ -82,13 +82,18 @@ scan, also after an aborted one, X returns to its normal move velocity.
 With `trigger_source="ddg"` the client shows a progress bar of the frames.
 
 To watch the measured positions while the scan runs, open the live plot of the
-exposure centres (Y versus X, one line after the other):
+exposure centres (Y versus X, forward and backward lines in two colours, updated
+after each line):
 
 ```python
-csaxs.aerotech.plot()                  # follows the running and the next scans
+csaxs.aerotech.plot()                  # shows the last scan, then follows the running and the next scans
 csaxs.aerotech.plot(scan_number=8494)  # a finished scan
+csaxs.aerotech.stop_plot()             # stop following (the plot stays)
 ```
 
+Every exposure is shown. The thin lines connect the points of each cell column; they
+only guide the eye.
+
 ### Examples
 
 Fields of view centred on the current position (`relative=True`), X fast, Y step: