fix: drop spots_indexed from no-crystal guard

Indexing was removed from the crystal score (w_indexed=0.00), so it must
not act as a hard veto either: a crystal that diffracts but fails to
index should still be targeted, not routed to grid centre. Guard now
checks max spots_low_res only.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/aarecommon/math/find_xtal.py

@@ -323,24 +323,24 @@ def raster_centre_of_mass(result_array, images) -> CenterOfMassModel | None:
     return _to_com_model(com, images, "Center of mass")
 
 
-def raster_highest_score(
-    images, min_low_res_spots: float = 10.0, min_spots_indexed: int = 1
-) -> CenterOfMassModel | None:
+def raster_highest_score(images, min_low_res_spots: float = 10.0) -> CenterOfMassModel | None:
     """Target the grid cell with the highest crystal score.
 
     If the whole grid is too weak to hold a crystal — max spots_low_res below
-    min_low_res_spots OR max spots_indexed below min_spots_indexed — target the
-    geometric centre of the grid instead of collecting at a noisy cell, so a
-    'nothing here' result is centred and deliberate rather than random noise.
+    min_low_res_spots — target the geometric centre of the grid instead of
+    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)
-    max_indexed = max((getattr(img, "spots_indexed", 0) or 0 for img in images), default=0)
-    if max_low_res < min_low_res_spots or max_indexed < min_spots_indexed:
+    if max_low_res < min_low_res_spots:
         n_nx, n_ny = score_array.shape
         logger.info(
-            f"No crystal in loop (max spots_low_res={max_low_res} < {min_low_res_spots} "
-            f"or max spots_indexed={max_indexed} < {min_spots_indexed}); "
+            f"No crystal in loop (max spots_low_res={max_low_res} < {min_low_res_spots}); "
             f"targeting grid centre of {n_nx}x{n_ny} grid"
         )
         # get_com_mm maps index i -> (i+0.5)*step, so index (N-1)/2 is the true
@@ -689,9 +689,12 @@ if __name__ == "__main__":
     com = raster_highest_score(noise)
     assert (com.n_x, com.n_y) == (1.0, 1.0), com
 
-    # Strong low-res but nothing indexed anywhere -> OR rule routes to centre.
-    no_index = [_cell(x, y, 40, 0) for x in range(3) for y in range(3)]
+    # Strong low-res but nothing indexed anywhere -> still targets the best
+    # cell: indexing is dropped from the score (w_indexed=0.00) and must not
+    # veto a diffracting crystal.
+    no_index = [_cell(x, y, 12, 0) for x in range(3) for y in range(3)]
+    no_index[6] = _cell(2, 0, 40, 0)
     com = raster_highest_score(no_index)
-    assert (com.n_x, com.n_y) == (1.0, 1.0), com
+    assert (round(com.n_x), round(com.n_y)) == (2, 0), com
 
     print("find_xtal self-check passed")