Remove start and end boundary cursors from spectrogram display

[Copilot]

Removes the green boundary cursors (start/end edges) from the video node's spectrogram display while preserving the yellow middle cursor for playback position.

Changes

• Removed boundary cursor rendering (lines 772-794 in node/InputNode/node_video.py)
  • Eliminated start cursor (left edge, green)
  • Eliminated end cursor (right edge, green)
  • Preserved middle cursor (playback position, yellow)

The spectrogram window extraction, padding logic, and classification data flow remain unchanged.

# Before: Drew 3 cursors (green start, yellow middle, green end)
cv2.line(spectrogram_window, (start_cursor_col, 0), ..., (0, 255, 0), 2)  # removed
cv2.line(spectrogram_window, (end_cursor_col, 0), ..., (0, 255, 0), 2)   # removed
cv2.line(spectrogram_window, (indicator_col, 0), ..., (0, 255, 255), 2)  # kept

# After: Only middle cursor remains
cv2.line(spectrogram_window, (indicator_col, 0), ..., (0, 255, 255), 2)

Original prompt

supprimme le cursor start et le cursor stop de spectrogramme du node video

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