feat(perception): sky detector for outdoor navigation — Issue #307
- Add _sky_detector.py: SkyResult NamedTuple; detect_sky() with dual HSV
band masking (blue sky H∈[90,130]/S∈[40,255]/V∈[80,255] OR overcast
S∈[0,50]/V∈[185,255]), cv2.bitwise_or combined mask; sky_fraction over
configurable top scan_frac region; horizon_y = bottommost row where
per-row sky fraction ≥ row_threshold (−1 when no sky detected)
- Add sky_detect_node.py: subscribes /camera/color/image_raw (BEST_EFFORT),
publishes Float32 /saltybot/sky_fraction and Int32 /saltybot/horizon_y
per frame; scan_frac (default 0.60) and row_threshold (default 0.30) params
- Register sky_detector console script in setup.py
- 33/33 unit tests pass (no ROS2 required)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
sl-perception
e24c0b2e26