Add 3 segmentation classes for UAV_VisLoc: bare soil, rooftop, sports field

Analysis of scene 01 showed 29% background pixels, mainly caused by:
- Plowed/bare fields (no crop match) → add "bare soil and plowed field"
- Dark/textured roofs missed by "building" → add "roof and rooftop"
- Sports fields/playgrounds → add "sports field and playground"

Total: 11 → 14 classes. Palette extended with 3 new colors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/augmentor/io_utils.py

@@ -94,6 +94,9 @@ _FIXED_PALETTE = np.array([
     [100,  60, 120],  # 8:  railway      — purple
     [255, 165,   0],  # 9:  parking lot  — orange
     [200, 200, 200],  # 10: sidewalk     — light gray
+    [140, 100,  50],  # 11: bare soil    — dark tan
+    [180,  60,  60],  # 12: rooftop      — dark red
+    [50,  200, 150],  # 13: sports field — teal
 ], dtype=np.uint8)