fix: supply max image with not enough spots

src/aarecommon/math/find_xtal.py

@@ -326,9 +326,6 @@ def raster_highest_score(images, min_low_res_spots: float = 10.0) -> CenterOfMas
     collecting at a noisy cell, so a 'nothing here' result is centred and
     deliberate rather than random noise.
 
-    spots_indexed is deliberately not part of the guard: indexing was dropped
-    from the crystal score (w_indexed=0.00), so a crystal that diffracts but
-    fails to index must still be targeted, not routed to centre.
     """
     score_array = compute_crystal_score_array(images)
     max_low_res = max((getattr(img, "spots_low_res", 0) or 0 for img in images), default=0)
@@ -340,7 +337,9 @@ def raster_highest_score(images, min_low_res_spots: float = 10.0) -> CenterOfMas
         )
         # get_com_mm maps index i -> (i+0.5)*step, so index (N-1)/2 is the true
         # geometric centre of the grid for both odd and even N (and N==1).
-        return CenterOfMassModel(n_x=(n_nx - 1) / 2.0, n_y=(n_ny - 1) / 2.0)
+        y_pos = (n_ny - 1) / 2.0
+        x_pos = (n_nx - 1) / 2.0
+        return CenterOfMassModel(n_x=x_pos, n_y=y_pos, max_image=int(y_pos*n_nx+x_pos))
     return _to_com_model(_max_cell(score_array), images, "Highest score")
 
 
@@ -360,7 +359,7 @@ def has_sufficient_low_res_spots(result_array: np.ndarray, min_spots_low_res: fl
 
 
 def compute_crystal_score_array(
-    scan_results: list, w_bkg: float = 0.25, w_low_res: float = 0.75, w_indexed: float = 0.00
+    scan_results: list, w_bkg: float = 0.01, w_low_res: float = 0.99, w_indexed: float = 0.00
 ) -> np.ndarray:
     """Combine bkg (25%), spots_low_res (75%), and spots_indexed (00%) into a 0–100 score.