Port v5 scoring fixes: border penalty, valid-region clip

- score_candidate: border contact penalty (×0.60 for 1 edge, ×0.35 for 2+)
prevents dark vegetation at image borders from outscoring contained cave voids
- process_image: hard-clip final mask to actual illumination columns after
refine_mask, removing IR vignette/penumbra reintroduced by GrabCut or smoothing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

detect_cave.py

@@ -458,8 +458,25 @@ def score_candidate(mask, gray_f32, weight_map, left_col, right_col,
         if valid_score < 0.5:
             lateral_pen = 0.4
 
+    # Border contact penalty: true cave entrances are contained within the frame.
+    # Dark patches that bleed to an image edge are likely cast shadows or vegetation
+    # extending beyond the visible area, not a cave void.
+    bp = 3  # border margin in pixels
+    border_touches = int(
+        (mask[:bp, :] > 0).any()       # top
+        + (mask[-bp:, :] > 0).any()    # bottom
+        + (mask[:, :bp] > 0).any()     # left
+        + (mask[:, -bp:] > 0).any()    # right
+    )
+    if border_touches == 0:
+        border_mult = 1.0
+    elif border_touches == 1:
+        border_mult = 0.60
+    else:
+        border_mult = 0.35
+
     total = (additive * area_mult * solidity_mult
-             * texture_mult * vert_gate * lateral_pen)
+             * texture_mult * vert_gate * lateral_pen * border_mult)
 
     return {
         "total":          round(float(total), 4),
@@ -480,6 +497,8 @@ def score_candidate(mask, gray_f32, weight_map, left_col, right_col,
         "valid_score":    round(float(valid_score), 3),
         "mean_inside":    round(float(mean_inside), 3),
         "mean_outside":   round(float(mean_outside), 3),
+        "border_touches": border_touches,
+        "border_mult":    round(float(border_mult), 3),
     }
 
 
@@ -819,6 +838,7 @@ def process_image(input_path, output_dir):
           f"depth={scores['depth']:.2f}  "
           f"area_m={scores['area_mult']:.2f}  "
           f"sol={scores['solidity']:.2f}(×{scores['sol_mult']:.2f})  "
+          f"border={scores['border_touches']}(×{scores['border_mult']:.2f})  "
           f"in={scores['mean_inside']:.2f}±{scores['texture']:.2f}  "
           f"out={scores['mean_outside']:.2f}")
 
@@ -921,6 +941,15 @@ def process_image(input_path, output_dir):
         best_mask = gc_result
 
     refined = refine_mask(best_mask, gray_f32)
+
+    # Hard-clip final mask to the actual illumination columns (not the capped
+    # lc/rc) to exclude IR vignette/penumbra that GrabCut or contour smoothing
+    # may have reintroduced after the expansion clip.
+    if actual_lc > int(w * 0.05):
+        refined[:, :actual_lc] = 0
+    if actual_rc < int(w * 0.95):
+        refined[:, actual_rc + 1:] = 0
+
     draw_result(gray_u8, refined, scores,
                 out_r, out_m, out_dv,
                 wmap, pn,